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Quantum
Computing
Internet
Autonomous
Vehicles
Hardware
SEPTEMBER 2021 www.computer.org
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IEEE Computer Society Magazine Editors in Chief
Computer IEEE Intelligent Systems IEEE Pervasive Computing
Jeff Voas, NIST V.S. Subrahmanian, Marc Langheinrich, Università
Northwestern University della Svizzera italiana
Computing in Science
& Engineering IEEE Internet Computing IEEE Security & Privacy
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Laboratory and University
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2469-7087/21 © 2021 IEEE Published by the IEEE Computer Society September 2021 1
SEPTEMBER 2021 � VOLUME 7 � NUMBER 9
Long-distance
The distances between connectivity and the
quantum computers diversity of qubits
within a quantum farm are expected.
are relatively short.
The distances Qubits are most likely
Distance and Heterogeneity
between qubits within to be homogeneous. Step 3:
Silicon Qubit Printed Circuit a quantum computer Interconnecting
MCM Chip Board
are extremely short. Multiple
Qubits are Geographically
homogeneous. Step 2: Distributed
Interconnecting Quantum Farms
Multiple Quantum
Computers Within
Step 1: the Same Quantum
ng Interconnecting Farm
ss RF Wiring HarnessQuantum
Multiple
Processors Within
ds a Single Quantum
Ribbon Bonds
8 14 34
mps Computer
Coplanar Waveguide
ier Transition to MCM
Time
Quantum The Rise of The 5G
Access the Quantum Revolution:
Internet Expectations
Versus Reality
Quantum Computing
8 Quantum Access
ERIK DEBENEDICTIS
14 The Rise of the Quantum Internet
MARCELLO CALEFFI, DARYUS CHANDRA, DANIELE CUOMO, SHIMA
HASSANPOUR, AND ANGELA SARA CACCIAPUOTI
Internet
20 Principles and Elements of Governance of Digital
Public Services
VIRGILIO ALMEIDA, FERNANDO FILGUEIRAS, AND FRANCISCO GAETANI
25 The Rising Threat of Launchpad Attacks
MARKUS JAKOBSSON
Autonomous Vehicles
31 Right Code
GERARD J. HOLZMANN
34 The 5G Revolution: Expectations Versus Reality
NURA JABAGI, ANDREW PARK, AND JAN KIETZMANN
Hardware
42 High-Level Synthesis-Based Approach for Accelerating
Scientific Codes on FPGAs
RAMSHANKAR VENKATAKRISHNAN, ASHISH MISRA, AND
VOLODYMYR KINDRATENKO
47 Recent Advances in Compute-in-Memory Support
for SRAM Using Monolithic 3-D Integration
ZHIXIAO ZHANG, XIN SI, SRIVATSA SRINIVASA, AKSHAY KRISHNA
RAMANATHAN, AND MENG-FAN CHANG
Departments
4 Magazine Roundup
7 Editor’s Note: Moving Quantum Computing Forward
60 Conference Calendar
Subscribe to ComputingEdge for free at
www.computer.org/computingedge.
Magazine Roundup
T he IEEE Computer Society’s lineup of 12 peer-reviewed technical magazines covers cutting-edge topics
ranging from software design and computer graphics to Internet computing and security, from scien-
tific applications and machine intelligence to visualization and microchip design. Here are highlights from
recent issues.
fundamentally human in nature;
Jupyter helps humans think and
eCloud: A Vision for tell stories with code and data. The Caricature Expression
the Evolution of the Edge- authors illustrate this by describ- Extrapolation Based on
Cloud Continuum ing three dimensions of Jupyter: (1) Kendall Shape Space Theory
interactive computing, (2) compu-
The authors of this article from the tational narratives, and (3) the idea In this article from the May/June
May 2021 issue of Computer pres- that Jupyter is more than software. 2021 issue of IEEE Computer
ent a holistic vision for the edge- They illustrate the impact of these Graphics and Applications, the
cloud ecosystem, with the intent dimensions on a community of prac- authors propose a novel expres-
of spurring the creation of next- tice in earth and climate science. sion extrapolation method for
generation technologies for futur- caricature facial expressions
istic applications that operate at based on the Kendall shape
computational-perception speeds space, in which the key idea is
to convert sensed data to action- The Computer Programs of to introduce a representation
able knowledge. Charles Babbage for the 3D expression model to
remove rigid transformations,
The mathematician and inven- such as translation, scaling, and
tor Charles Babbage drafted 26 rotation, from the Kendall shape
Jupyter: Thinking and code fragments between 1836 space. Built on the proposed rep-
Storytelling With Code and 1840 for his unfinished “Ana- resentation, the 2D caricature
and Data lytical Engine.” The programs were expression extrapolation pro-
embedded implicitly in tables rep- cess can be controlled by the 3D
Project Jupyter is an open-source resenting execution traces. In this model reconstructed from the
project for interactive comput- article from the January–March input 2D caricature image and
ing that is widely used in data sci- 2021 issue of IEEE Annals of the the exaggerated expressions
ence, machine learning, and sci- History of Computing, the authors of the caricature images gener-
entific computing. The authors of explore the programming architec- ated based on the extrapolated
this article from the March/April ture of Babbage’s mechanical com- expression of a 3D model that is
2021 issue of Computing in Science puter, that is, its structure from robust to facial poses in the Ken-
& Engineering argue that even the point of view of a programmer, dall shape space; this 3D model
though Jupyter helps users per- based on those 26 coding exam- can be calculated with tools
form complex technical work, Jupy- ples preserved in the Babbage such as exponential mapping in
ter itself solves problems that are Papers Archive. Riemannian space.
4 September 2021 Published by the IEEE Computer Society 2469-7087/21 © 2021 IEEE
AI, signal processing, and crypto-
graphic applications. Interleaved-
Optimal Finite-Horizon AI-Driven Provisioning in the multithreading (IMT) processor
Perturbation Policy for 5G Core cores are interesting to pursue
Inference of Gene energy efficiency and low hard-
Regulatory Networks Network slicing enables com- ware cost for edge computing,
munication service providers to yet they need hardware acceler-
A major goal of systems biology is partition physical infrastructure ation schemes to run heavy com-
to model accurately the complex into logically independent net- putational workloads. Following
dynamical behavior of gene regu- works. Network slices must be a vector approach to accelerate
latory networks (GRNs). Despite provisioned to meet the service- computations, this article from
several advancements that have level objectives (SLOs) of dispa- the March/April 2021 issue of IEEE
been made in inference of GRNs, rate offerings. Network orches- Micro explores possible alterna-
two main issues continue to make trators must customize service tives to implement vector copro-
the problem challenging: (1) non- placement and scaling to achieve cessing units in RISC-V cores,
identifiability of parameters and the SLO of each network slice. In showing the synergy between IMT
(2) limited amounts of data. Thus, it this article from the March/April and data-level parallelism in the
becomes necessary to experimen- 2021 issue of IEEE Internet Com- target workloads.
tally perturb or excite the system puting, the authors discuss the
into different states. This perturba- challenges encountered by net-
tion process disrupts the expres- work orchestrators in allocating
sion of genes from active to inac- resources to disparate 5G net- Feature-Guided Spatial
tive, or vice versa, at each time work slices. They propose the use Attention Upsampling
point. Another issue is the partial of artificial intelligence to make for Real-Time Stereo
observability of the gene states, core placement and scaling deci- Matching Network
which must be inferred indirectly sions that meet the requirements
from noisy gene expression mea- of network slices deployed on In this article from the January–
surements. In this article from the shared infrastructure. March 2021 issue of IEEE MultiMe-
January/February 2021 issue of IEEE dia, the authors propose an end-
Intelligent Systems, the latter issue to-end real-time stereo matching
is accounted for by employing the network (RTSMNet). RTSMNet
partially observed Boolean dynami- Klessydra-T: Designing consists of three modules. The
cal system signal model for the data Vector Coprocessors global and local feature extrac-
and applying optimal state estima- for Multithreaded Edge- tion (GLFE) module captures the
tion. Then, the optimal finite-hori- Computing Cores hierarchical context information
zon perturbation policy is derived and generates the coarse cost
to achieve the highest possible Computation-intensive kernels, volume. The initial disparity esti-
expected performance for the such as convolutions, matrix multi- mation module is a compact 3D
maximum a posteriori estimator plication, and Fourier transform, are convolution architecture aim-
under a small perturbation cost. fundamental to edge-computing ing to produce the low-resolution
www.computer.org/computingedge 5
MAGAZINE ROUNDUP
(LR) disparity map rapidly. The through highly engaging experi-
feature-guided spatial attention ences. The rapid rise of educa-
upsampling module takes the LR A Systems Approach Toward tional escape rooms has led to
disparity map and the shared fea- Addressing Anonymous a misalignment between educa-
tures from the GLFE module as Abuses: Technical and tors’ needs for being able to imple-
guidance, first estimates resid- Policy Considerations ment this novel teaching prac-
ual disparity values and then an tice and the availability of tools
attention mechanism is devel- Can we prevent the abuses of anon- to ease the process. Moreover,
oped to generate context-aware ymous communication networks this lack of support is preventing
adaptive kernels for each upsam- without affecting their ability to teachers and students from tak-
pled pixel. enhance privacy and evade censor- ing full advantage of the potential
ship? The authors of this article of educational escape rooms. This
from the March/April 2021 issue article from the March/April 2021
of IEEE Security & Privacy evaluate issue of IT Professional provides
approaches for balancing the need a road map of the most urgent
The Road to Ubiquitous for anonymity with the desire to issues to be addressed to bridge
Personal Fabrication: mitigate anonymous abuses. the aforementioned gap: easing
Modeling-Free Instead of the creation of digital puzzles, aid-
Increasingly Simple ing in the logistical aspects of con-
ducting an educational escape
The authors of this article from Automatic Recovery of room, harnessing learning ana-
the January–March 2021 issue of Missing Issue Type Labels lytics, fostering remote collabo-
IEEE Pervasive Computing argue ration, and integrating artificial
that to achieve similar outreach Agile software organizations intelligence to adapt the experi-
and impact as personal comput- em
power developers to make ence to each team.
ing, personal fabrication research appropriate decisions rather than
may have to venture beyond ever- enforce adherence to a process,
simpler interfaces for creation, resulting in incomplete and noisy
toward lowest-effort workflows data in software archives. Since
for remixing. The authors sur- software analytics techniques
veyed novice-friendly digital fab- are trained using this data, auto- Join the IEEE
rication (DF) workflows from the mated techniques are required to Computer
perspective of HCI. Through this recover it. Read more in this arti-
Society
survey, they found two distinct cle from the May/June 2021 issue
approaches for this challenge: (1) of IEEE Software. computer.org/join
simplifying expert modeling tools
and (2) enriching tools not involv-
ing primitive-based modeling with
powerful customization. They Technology-Enhanced
argue that to be able to include Educational Escape Rooms:
the majority of the population A Road Map
in DF, research should embrace
omission of workflow steps, shift- Educational escape rooms have
ing toward automation, remixing, emerged as a new type of teach-
and templates, instead of model- ing practice with the promise
ing from the ground up. of enhancing students’ learning
6 ComputingEdge September 2021
Editor’s Note
Moving Quantum
Computing Forward
I n the past few years, quantum
computing has gone from theo-
retical science to promising tech-
challenges involved in designing a
quantum network infrastructure,
such as reformulating information
testing can improve reliability in
autonomous vehicle software. In
IT Professional’s “The 5G Revolu-
nology with many real-world appli- transmission and interconnecting tion: Expectations Versus Real-
cations. Quantum computing is quantum processors. ity,” the authors predict that 5G’s
being used to make transporta- Digital literacy and effective ultra-low latency will help enable
tion and scientific discovery more use of the Internet are essen- fully autonomous vehicles.
efficient, and myriad other use tial skills. IEEE Internet Comput- This ComputingEdge issue
cases are on the horizon. How- ing’s “Principles and Elements of concludes with two articles on
ever, a lot of work remains before Governance of Digital Public Ser- hardware for high-performance
quantum computing can reach its vices” examines the government’s computing (HPC). “High-Level
full potential. Two articles from role in expanding digital literacy Synthesis-Based Approach for
Computer focus on what it will and Internet access. IEEE Secu- Accelerating Scientific Codes on
take to further develop and lever- rity & Privacy’s “The Rising Threat FPGAs,” from Computing in Sci-
age quantum computing. of Launchpad Attacks” provides ence & Engineering, describes
“Quantum Access” pres- background on online social engi- design platforms for HPC on FPGA
ents a vision for giving students, neering and gives advice on how hardware. “Recent Advances in
researchers, and start-up compa- to protect against such attacks. Compute-in-Memory Support for
nies access to quantum hardware, Autonomous vehicles are SRAM Using Monolithic 3-D Inte-
allowing more people to contrib- becoming more prevalent in our gration,” from IEEE Micro, explores
ute to the advancement of quan- society. In IEEE Software’s “Right an approach for improving hard-
tum computing. “The Rise of the Code,” the author asserts that self- ware performance for data-inten-
Quantum Internet” details the checking code and requirements sive applications.
2469-7087/21 © 2021 IEEE Published by the IEEE Computer Society September 2021 7
EDITOR: Erik P. DeBenedictis, Zettaflops, LLC, erikdebenedictis@gmail.com
This article originally
appeared in
DEPARTMENT: REBOOTING COMPUTING
vol. 53, no. 10, 2020
Quantum Access
Erik DeBenedictis, Zettaflops, LLC
Quantum computers are available via the Internet for students and small-scale
research. What if similar access could be extended to quantum hardware?
I
took a class on integrated circuit design when in an IEEE Quantum Initiative working group, and I’m
I was a student in 1981. The class project was for writing about it here as a noncommercial concept
each student to design and test a CMOS circuit. that IEEE Members could champion in the public
I designed a CMOS arbiter, a circuit used to reliably interest.
detect which of two input signals arrives first. The chip
was fabricated as part of a multiproject wafer during A BRIEF HISTORY OF
the first run of ARPA’s (now DARPA’s) MOS Imple- INTEGRATED CIRCUITS
mentation Service (MOSIS) and delivered to me as a Integrated circuits were originally designed by cut-
chip bonded into a package—like a simplified version ting plastic such as Rubylith and handcrafting what
of the one shown in Figure 1—and I tested it with an were essentially photographic negatives. The meth-
oscilloscope. od’s scale-up limitations are obvious. At some point,
However, the version shown in Figure 1 is a quan- companies started writing their own computer-aided
tum module built by a professional research team1 design (CAD) software, which codified design rules
out of components created by governmental and such as the minimum dimensions of wires or tran-
commercial fabricators (fabs) that could become sistors and the various spacings between them. The
the quantum equivalent of my 1981 CMOS chip. The design processes were proprietary because they
central gray box in Figure 1 contains qubits bonded gave the electronics manufacturer that sold the chips
on top of a somewhat larger classical electronics a competitive advantage in speed, density, and reli-
chip. Unlike my 1981 chip, some of the leads in Figure ability. Proprietary design processes preserved this
1 carry microwave signals, and the module operates competitive advantage but meant that the employ-
at millikelvins. Although the module in Figure 1 is not ees had to be trained on the job.
a complete quantum computer, its structure and the To make the semiconductor industry scalable,
process of creating it would give students hands-on universities championed relaxed “least common
experience or support experimental research proj- denominator” design rules that were independent of
ects within the bounds of the module’s external any specific process.2 Process-independent design
interfaces. rules would work on proprietary fab lines, thus fore-
Quantum technology is roughly as mature as shadowing the emergence of a separate CAD industry,
CMOS was in 1981, making it feasible to offer students semiconductor foundries, and a systematic way to
and small research groups access to quantum hard- train the workforce that has engineered all of the chips
ware prototyping. This concept has been discussed in use today.
ARPA’s MOSIS made chip design widely accessible.
The main idea was that students from many universi-
Digital Object Identifier 10.1109/MC.2020.3011079 ties would create chip designs using generic design
Date of current version: 5 October 2020 rules as class projects or for theses. Student designs
8 September 2021 Published by the IEEE Computer Society 2469-7087/21 © 2021 IEEESilicon Qubit Printed Circuit
MCM Chip Board
dc Wiring
Harness RF Wiring Harness
Wire Bonds
Ribbon Bonds
Microbumps
Coplanar Waveguide
Metal Carrier Transition to MCM
FIGURE 1. A hybrid classical-quantum module.1 The small square indicated contains two qubits, and the larger square below it
contains single-flux quantum logic. The test fixture carries both dc and microwave signals. RF: radio frequency; MCM: mul-
tichip module.
are typically so small that the overhead of commercial ›› fabricates quantum components like those
contracting is burdensome; therefore, many student shown in Figure 1, using unique quantum fea-
designs could be combined into a single fab run. The tures such as cryogenic packaging, microwave
MOSIS operational model is one in which the layout signals, qubits, and control electronics, extend-
from multiple student projects would be combined by ing the suite of available features over time as
the MOSIS operator into a single set of masks and then discussed later in this article
manufactured by any foundry that could support the ›› at the operational level, the operator would
generic design rules. contract with fabs, design tool suppliers, and
MOSIS is in operation today (https://mosis.com) companies that can perform certain assembly
and the main chip fab option available to students. But activities, essentially aggregating funds from
it is also a practical option for start-ups and, in fact, small users to create a fab run that is compatible
any researcher who wants to create a handful of small with standard industrial processes
chips to test a hardware idea. ›› organizes, but does not create, educational
materials, process design kits (PDKs), and
QUANTUM ACCESS generic intellectual property (IP) that enables
Quantum computer systems are now accessible users to get up to speed quickly.
via the Internet for quantum software training and
small-scale research. Extending access to quantum The quantum access user would be a student,
hardware could follow and then extend the semicon- researcher, or start-up company that wants to try out
ductor MOSIS paradigm. The IEEE Quantum Initiative a hardware idea in quantum information technology.
is using the name quantum access for a potential non- Student interest would start by taking classes, perhaps
profit service that those specifically developed for quantum access. All
www.computer.org/computingedge 9REBOOTING COMPUTING
TABLE 1. The quantum access user classes.
Segment Objectives Typical interaction Technology and IP
Students Hands-on experience to University uses educational Educational modules where indicated; a
augment classwork materials that highlight the use of standard PDK and generic IP from others;
quantum access; submits simple little interest in commercializing the IP
components from the class project students create
for fab
University Foundry for trying out Fab using standard processes with May modify the PDK or create a new
research novel ideas for a thesis new designs; researcher may go on one; interest in IP for publication or
or for faculty research site commercialization through university
projects licensing
Commercial users Prototyping hardware Fab using standard processes with May modify the PDK; the design may be
concepts, R&D new designs; employees may go on commercially sensitive and must be kept
missions, and derivative site from other user; new IP will be owned by
technology the user
Government Prototyping Requests from government research Standard or government-supplied PDKs;
agencies nonstandard technology programs; researchers may go on the latter could be released commercially
site as well as government program over time; government IP may be sensitive
administrators
Government Exploring high-risk or Fab request directly from a Standard or government-supplied PDKs;
research labs niche technology that government entity government may create a fab; government
may not be destined for IP may be sensitive but may not be
commercialization intended for commercialization
(Original table courtesy of Synopsys; modified by the author.)
users would then require access to a capital-intensive cryogenic). This would enable the user (or the user’s
fab and help construct a “test harness,” that is, a university or employer) to place an order for commer-
simple system, to test an idea. Table 1 summarizes the cially available equipment and have some assurance
different user classes. that the purchased parts would work together and
To try out the idea quickly and at low cost, quan- also work with the custom parts created by quantum
tum access would also curate information about access’s foundries. Unlike the situation I experienced
the design of standard components, called IP, which in 1981, it may be possible for a cryogenic test sys-
tem to be constructed on a centralized location and
accessed via the Internet.
UNLIKE THE SITUATION I Quantum access should anticipate that a few
EXPERIENCED IN 1981, IT MAY BE projects will become unusually successful and provide
POSSIBLE FOR A CRYOGENIC TEST a path to volume manufacturing. Thus, start-ups, the
SYSTEM TO BE CONSTRUCTED ON government, and government labs would have a role
A CENTRALIZED LOCATION AND that eventually outgrows the quantum access model;
ACCESSED VIA THE INTERNET. these are listed near the bottom of Table 1.
QUANTUM ACCESS
users could include with no modification and hence MATURATION PROCESS
with less effort or risk of error. For example, users with It didn’t occur to me in 1981 to ask which semiconduc-
ideas for a new microwave amplifier can prototype tor process would be used for my CMOS MOSIS chip.
their innovative amplifier circuit but use open source, I was simply glad there was one option instead of no
tested designs for filters, drivers, and so on. options. Quantum access could start out similarly by
Quantum access would also be a source of reliable supporting a single quantum-system type (for exam-
information about physical test apparatus (including ple, a qubit type) and expand the number of types over
10 ComputingEdge September 2021REBOOTING COMPUTING
time. As an example of where this might go, the semi- are cryo CMOS and superconducting electronics
conductor MOSIS service currently supports 20 semi- based on classical JJs.
conductor processes from two foundries. For example, Intel and Microsoft fund quantum
control electronics using existing CMOS processes
QUBITS of a modest linewidth (for example, 28 nm) and that
Superconducting qubits (transmons) seem to have are in commercial use for the Internet of Things
reached the maturity level necessary for quantum and other timely business opportunities. 3,4 Many
access to be viable. Transmons are physically large and room-temperature semiconductor processes work
do not require many mask layers, making current designs at cryogenic temperatures, although some work bet-
mature enough for general production. Although ter than others. It is expected that, over time, special
research on superconducting qubits continues, the cryo CMOS processes will be developed for quantum
quantum industry is growing and expected to special- information, further differentiating quantum access
ize as it matures, so some students and new corporate from MOSIS. Lincoln Labs, SeeQC, Skywater, and
or university entrants may want to avoid well-trodden others use JJ-based control circuitry,1,5 which has
areas, such as making their own qubits. Instead, they different properties in terms of density, heat dissipa-
might use generic qubits for research projects in other tion, and so forth.
areas under the assumption that their results would Unlike the simple fab processes used by transmon
be combined with the latest qubits prior to production.
Even though specific plans are yet to be deter-
mined, ion traps may be the second qubit type EXPERIMENTAL ION TRAPS USED
offered. Experimental ion traps used for quantum FOR QUANTUM COMPUTER-TYPE
computer-type applications are manufactured by gov- APPLICATIONS ARE MANUFACTURED
ernment labs. Some of these labs fabricate for other BY GOVERNMENT LABS.
parties, although foundry access will need to mature
before ion traps will be viable in quantum access.
qubits, classical control systems will have roughly the
CLASSICAL CONTROL SYSTEMS same process complexity (for example, the number of
Transmon systems are almost universally controlled layers) as that of today’s CMOS, implying an expensive
by room-temperature lab equipment interfacing via fab. JJ processes are destined to be equally complex
electronics at various temperature stages. The elec- but are still under development, including through
tronics may be passive, transistor, or Josephson junc- government R&D funding. When it is time to support
tion (JJ) based. ion traps, quantum access would need to embrace a
Just as I tested my CMOS chip in 1981 using an different fab process, electronics with different oper-
oscilloscope, the idea is that quantum access would ating voltages, optical (laser) signaling, and optical
engage with test equipment and cryogenic equip- components.
ment manufacturers from the start. Although quan-
tum technology is not ready for formal standards, DESIGN TOOLS AND IP
researchers need information on signal flow through Integrated circuits have not been designed directly by
cryogenic stages and what to expect from test equip- humans for decades, but rather by electronic design
ment. Test equipment and cryogenics will inevitably automation (EDA) software that synthesizes circuits,
evolve; therefore, these manufacturers are expected translates them into physical layouts, and then simu-
to be interested in feedback from users. lates their performance. Thus, new quantum-relevant
As quantum technologies mature, there is the design principles will need to be embedded into design
belief that room-temperature lab equipment will be tools. It will be essential that industry fosters the devel-
supplemented by electronics close to the qubits for opment of quantum-specific design tools and dissem-
reasons of signal latency, bandwidth, and thermal inates to the quantum workforce the knowledge for
backflow. Broadly speaking, the two leading options how to use them.
www.computer.org/computingedge 11REBOOTING COMPUTING
The idea is that quantum access would work with ACKNOWLEDGMENTS
EDA companies to ensure that students and other Although references made to my 1981 MOSIS project
users have the most advanced and compatible tools are entirely my responsibility, quantum access is the
available from industry to produce designs for quan- topic in a semiformal IEEE Quantum Initiative work-
tum access. Quantum access would also serve as a ing group. The ideas herein are due to approximately a
repository for open access hardware designs, subject dozen people in that group. Individuals from Raytheon,
to limitations on the distribution of this information Baylor University, Syracuse University, the Massachu-
due to proprietary or government restrictions. setts Institute of Technology, and Synopsys assisted
with preparing this article.
EDUCATIONAL MATERIALS
Although quantum access is not expected to dis- REFERENCES
tribute educational materials directly, it may end up 1. R. Das et al., “Cryogenic qubit integration for quantum
with a central role in making educational materials computing,” in Proc. 2018 IEEE 68th Electronic Compo-
effective. Future quantum engineering students nents and Technology Conf. (ECTC), pp. 504–514. doi: 10
will need to take classes on the design of qubits and .1109/ECTC.2018.00080.
various forms of control electronics. These classes 2. C. Mead and L. Conway, Introduction to VLSI Systems,
would teach best practices and have a role in defin- vol. 1080. Reading, MA: Addison-Wesley, 1980.
ing the terminology, circuits, and so forth that stu- 3. B. Patra et al., “A scalable Cryo-CMOS 2-to-20GHz
dents bring to the workforce after they gradu- digitally intensive controller for 4 × 32 frequency
ate. The developers of educational materials could multiplexed spin qubits/transmons in 22nm FinFET
coordinate with quantum access to ensure that stu- technology for quantum computers,” in Proc. 2020 Int.
dents do homework assignments and class proj- Solid-State Circuits Conf., pp. 304–306. doi: 10.1109
ects in ways that are not just generally correct but /ISSCC19947.2020.9063109.
compatible with the specific methods and customs 4. S. J. Pauka et al., A cryogenic interface for controlling
used in industry. many qubits. 2019. [Online]. Available: arXiv:1912.01299
If experience with the semiconductor MOSIS 5. R. McDermott et al., “Quantum–classical interface
activity decades ago recurs, quantum access could based on single flux quantum digital logic,” Quantum
influence the development of an industrial quantum Sci. Technol., vol. 3, no. 2, p. 024004, 2018. doi: 10.1088
infrastructure and, possibly, standards in the quantum /2058-9565/aaa3a0.
engineering domain.
I t seems natural that the quantum industry will
develop commercial infrastructure similar to the
existing semiconductor industry, including fabs, fab-
ERIK DEBENEDICTIS is the principal of Zettaflops, LLC,
editor-in-chief of IEEE Transactions on Quantum Engineer-
ing, and a volunteer supporting the IEEE Computer Society,
less design houses, design tool vendors, and IP sup- Council on Superconductivity, Rebooting Computing, and
pliers, all of which would be coordinated by standards. Quantum Initiative. Contact him at erikdebenedictis@gmail
Yet, the industry can and should partner with noncom- .com.
mercial organizations, such as IEEE, the Quantum Eco-
nomic Development Consortium, universities, and, we
suggest here, a new quantum access entity.
Building a fab costs a lot of money, yet the quan-
tum access concept does not involve building fabs.
Instead, it organizes people to cooperate toward the
common goal of educating students and supporting F O LLOW US
early-stage research, both of which are imperative and @ s e cu rit y p riv a c y
worthwhile goals. This article describes a worthwhile
goal in the hope that readers will lend support.
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revised 25 May 2021EDITOR: Erik P. DeBenedictis, Zettaflops, LLC, erikdebenedictis@gmail.com
This article originally
appeared in
DEPARTMENT: REBOOTING COMPUTING
vol. 53, no. 6, 2020
The Rise of the Quantum Internet
Marcello Caleffi, Daryus Chandra, Daniele Cuomo, Shima Hassanpour, and
Angela Sara Cacciapuoti, University of Naples Federico II
The Internet just turned 50: five decades that shaped the world we live in. But what
comes next, the so-called Quantum Internet, will be even more revolutionary, likely in
ways we can’t imagine yet.
O
n 29 October 1969, the first successful mes- to participate in the so-called quantum race. Several
sage was exchanged over the Arpanet, the start-up companies also have been founded to join
predecessor to what we now know as the in this monumental endeavor. A very significant mile-
Internet. In the five decades since, the Internet has stone was achieved at the end of 2019 by a group of
revolutionized communications to the extent that its researchers at Google, which announced quantum
impact on our lives is not only technological but rather supremacy by solving a classically intractable prob-
has affected almost every facet of business and life- lem with its quantum processor7,8 (see “The Quantum
style, throughout the structure of society. Supremacy”).
The Internet itself evolved amazingly during these Immense interest in the future of quantum tech-
decades, from a network comprising a few static nodes nologies is not only displayed by industry but also
in the early days to a leviathan interconnecting half of by governments around the world. To mention some
the world’s population through billions of devices. Yet initiatives, in April 2017, the European Commission
the fundamental underlying assumption—the Inter- launched a 10-year, €1 billion flagship project to accel-
net’s primary purpose of transmitting messages that erate European quantum technologies research.9
can be successfully encoded in a sequence of classical Meanwhile, across the Atlantic, in September 2018, the
bits—has been unchanged since the beginning. U.S. House of Representatives unanimously approved
The advent of the engineering phase of quantum the establishment of a National Quantum Initiative
technologies is challenging the Internet’s fundamen- funded with US$1.25 billion over 10 years.10
tal assumption because quantum devices require—as Within this context of a real quantum revolution,
communication primitives—the ability to transmit the ultimate vision is to build a quantum network infra-
quantum information. Hence, research groups structure—also known as the Quantum Internet—to
throughout the world, and ours as well, are investing interconnect remote quantum devices so that quan-
their efforts to design and engineer the Quantum tum communications among them are enabled.2,3 The
Internet.1–6 But there’s still a long way to go and no reason behind this vision is that the Quantum Internet
guarantee of getting there very soon. is capable of supporting functionalities with no direct
counterpart in the classical Internet—ranging from
THE QUANTUM REVOLUTION secure communication5 to blind computing 11 through
Quantum technology advances have successfully distributed quantum computing 1,2—as recently over-
enticed tech giants, such as IBM, Google, and Intel, viewed by the Internet Engineering Task Force.12
Although it is too early to tell when and how this
quantum network will be deployed, our goal here is
Digital Object Identifier 10.1109/MC.2020.2984871 to describe how the Quantum Internet differs from
Date of current version: 4 June 2020 the current Internet. For this, we introduce the very
14 September 2021 Published by the IEEE Computer Society 2469-7087/21 © 2021 IEEEbasic idea of the Quantum Internet and its underlying
foundation, and we highlight the necessary steps as
well as the novel challenges we will face on our journey THE QUANTUM
toward the Quantum Internet design and deployment. SUPREMACY
THE QUANTUM INTERNET
The Quantum Internet is a network enabling quantum
communications among remote quantum devices.
T he term quantum supremacy was coined by
J. Preskill in 2011S1 to describe the moment
when a programmable quantum device would solve
What sets it apart from the classical Internet is the a problem that cannot be solved by classical com-
ability to transmit quantum bits (qubits), which dif- puters, regardless of the usefulness of the problem.
fer fundamentally from classical bits, and create dis-
REFERENCE
tributed, entangled quantum states with no classical
S1. J. Preskill, “Quantum computing and the
equivalent.3 entanglement frontier,” in Proc. 25th Solvay
Specifically, the Quantum Internet is governed by Conf. Physics, Oct. 2011.
the laws of quantum mechanics. Hence, phenomena
with no counterpart in classical networks, such as
entanglement, the impossibility to safely read and
copy the quantum information impose terrific con-
straints for the network design. That means most THE DIRECT TRANSMISSION OF
techniques adopted within the classical Internet can- QUBITS SO FAR APPEARS LIMITED
not be reused here.2 TO RELATIVELY SHORT DISTANCES
Just consider how important storing information IN THE CONTEXT OF SPECIFIC
for long periods at network nodes is to classical Inter- APPLICATIONS THAT CAN TOLERATE
net functionalities. This cannot be taken for granted LOW-TRANSMISSION SUCCESS RATES.
in the Quantum Internet because the phenomenon
known as decoherence rapidly corrupts quantum
information, making it challenging to rely on quantum makes its state collapse into a classical bit value—0
memories. or 1. For this particular reason, and for the no-cloning
Another constraint that makes things harder is theorem as well, the direct transmission of qubits so
the no-cloning theorem. Indeed, the classical Inter- far appears limited to relatively short distances in
net operates by extensively duplicating information the context of specific applications that can tolerate
among the different components of a network node low-transmission success rates.
and among different nodes. In the Quantum Internet, It becomes evident that a paradigm shift is required.
the no-cloning theorem forbids copying an unknown Indeed, the very concept of information transmission has
qubit. Hence, the commonly used methods for keep- to be rethought and reformulated for Quantum Inter-
ing the integrity of information, for example, retrans- net design. Thankfully, quantum mechanics provides us
mission of the same information, are now forbidden. an amazing tool for transmitting quantum information,
Finally, quantum states cannot be read without the quantum teleportation process, astonishingly,
affecting their states. Any attempt to measure a qubit without the physical transfer of the qubit.
www.computer.org/computingedge 15REBOOTING COMPUTING
Sender
Original
Quantum State Entanglement”), in 1993 Bennett
et al.13 showed that it is possible to
Classical instantaneously transfer the quan-
Communication tum state encoded in a qubit at a
certain sender to a qubit stored at
a certain receiver without, surpris-
EPR Pair ingly, the physical transfer of the
qubit at the sender.3 This quantum
Receiver communication protocol, already
experimentally verified, is known
as quantum teleportation.
In a nutshell, the teleportation
process, portrayed in Figure 1 for a
Two-Qubit Operations One-Qubit Operations Measurement single qubit, requires 1) the genera-
tion and distribution of a maximally
FIGURE 1. A general schematic of quantum teleportation protocol, where the entangled pair of qubits (referred
standard bra-ket notation |· is adopted for describing quantum states. Notice in the to as an EPR pair) between the
figure that after quantum teleportation, the original qubit and the entanglement are source and destination, and 2)
destroyed. As weird as it seems, quantum teleportation fully obeys the fundamen- a classical transmission to send
tal principles of quantum mechanics. Therefore, the cost of transmitting quantum two classical bits. Consequently, a
information can be exchanged with entanglement and classical communications. classical link for sending classical
Because the entanglement is always destroyed after every single teleportation, information and a quantum link for
it constitutes the primary consumable resource in the Quantum Internet, which entanglement generation and dis-
means it needs to be generated continuously. tribution need to be established in
advance.
Moreover, each teleportation
process destroys the entanglement-pair member at
the source. A successive teleporting requires the
INTRODUCING generation and distribution of a new entangled pair
ENTANGLEMENT between source and destination. This, in turn, implies
E
radically new challenges from a network design per-
ntanglement is one of the most distinguishing spective, completely changing the classical concepts
quantum phenomena with no counterpart in
of network connectivity and throughput. Indeed, the
the classical world, in which the quantum states of
connectivity between two quantum nodes is strictly
two or more particles become inextricably linked
even if they are separated by a great distance. The
determined by the availability of a shared entangled
entanglement of quantum particles demonstrates pair, and it inherently varies in time as a consequence
a relationship between their fundamental proper- of the depletion of the entanglement-pair member at
ties that cannot happen arbitrarily. When a mea- the source.
surement is performed on one of the particles, the The challenges are not limited to the above-
other particle will be instantly influenced. mentioned ones. In fact, long-distance entanglement
distribution still constitutes a key issue due to the
decay of the entanglement distribution rate as a func-
tion of the distance.1,3 And because qubits cannot be
BEYOND DIRECT QUBIT copied due to the no-cloning theorem, classical signal
TRANSMISSION amplification techniques cannot be employed. In this
By using a unique feature of quantum mechan- context, quantum teleportation relies on intermediate
ics, known as entanglement (see “Introducing nodes, known as quantum repeaters, that are capable
16 ComputingEdge September 2021REBOOTING COMPUTING
Quantum Device 1 Quantum Repeater Quantum Device 2
(4) Local (2) Bell-State (4) Local
Operation (3) Classical Measurement (3) Classical Operation
Communication Communication
(a) (1) EPR Pair (1) EPR Pair
Quantum Device 1 Quantum Repeater Quantum Device 2
Classical Link Classical Link
(b) Entangled Qubits Over a Longer Link
FIGURE 2. The entanglement swapping portrait. (a) Each quantum device shares an EPR pair with an intermediate node, the
quantum repeater. The repeater performs Bell-state measurement on the two qubits in its possession, which results in the col-
lapse of their quantum states into classical bits. The repeater sends the classical bits obtained from the measurement opera-
tion to the quantum devices. Finally, based on the received bits, the quantum devices perform local operations to complete the
swapping process. (b) The result is that the entanglement between the quantum devices is created over a longer distance.
of entangling distant nodes—without physically send-
ing an entangled qubit through the entire distance—
by swapping the entanglement generated through REALIZING THE QUBIT
shorter links,14 as illustrated in Figure 2.
It is evident that the design of the Quantum Inter-
net constitutes a breakthrough from an engineering
perspective. Each network functionality must be
C urrently, there exist multiple technolo-
gies for realizing a qubit (quantum dots,
transmons, ion traps, photons, and so forth),
redesigned and reengineered with a solid integra- with each technology characterized by different
tion of classical and quantum communications pros and cons. This hardware heterogeneity will
impose its own additional challenges to create
resources.15 In this regard, the classical resources
an integrated Quantum Internet ecosystem.
for transmitting classical bits will likely be provided
by integrating such classical networks as the current
Internet with the Quantum Internet. 2
P aving a journey toward the Quantum Internet is
indeed not a straightforward task. Historically,
predictions about technological developments prove
However, we may envision roughly three subse-
quent necessary steps, whose complexity scales
themselves true hardly or in ways the predictor didn’t as a function of the time and the level of platform
expect at all. Hence, there will definitely be twists heterogeneity, as portrayed in Figure 3. The very
and turns in the design of the Quantum Internet, with first step involves interconnecting multiple quan-
uncertainty on when and how this goal will be accom- tum processors within a single quantum computer.
plished (see “Realizing the Qubit”). The qubits are likely to be homogeneous among the
www.computer.org/computingedge 17REBOOTING COMPUTING
Long-distance The second step involves
The distances between connectivity and the
quantum computers
interconnecting multiple quan-
diversity of qubits
within a quantum farm are expected.tum computers within the same
are relatively short. farm. At this stage, the hardware
The distances Qubits are most likely
Distance and Heterogeneity
between qubits within to be homogeneous.
Step 3: heterogeneity among the different
a quantum computer Interconnecting quantum computers may arise.
are extremely short. Multiple
Qubits are Geographically Such heterogeneity must be con-
homogeneous. Step 2:
Distributed sidered in network functionalities.
Interconnecting Quantum Farms
The entanglement distribution
Multiple Quantum
Computers Within benefits from the controlled farm
Step 1: the Same Quantum
Interconnecting environment and relatively short
Farm
Multiple Quantum distances. Delay imposed by
Processors Within
a Single Quantum classical communication times
Computer is slightly longer compared to
interprocessor wiring. Hence,
this requires more sophisticated
timing and synchronization. The
Time
network topology is more com-
plex, and it may vary in time as the
FIGURE 3. The necessary steps toward the envisioned Quantum Internet. We number of nodes in the network
hypothesize that the complexity scales proportional to the distance of connectivity changes. This, in turn, induces
and level of platform heterogeneity among quantum farms. dynamics at the network boot-
strap/functioning, which requires
more sophisticated strategies for
different processors, although heterogeneity may routing and access as well as for mitigating quantum
arise within due to different hardware technolo- errors. Finally, the balance between local and remote
gies underlying memory and computational units. operations—between computational and communi-
The link for connecting the qubits is very short, and cation qubits—becomes even more intricate.
the network topology is fixed so that only a simple The final long-term step involves interconnect-
addressing and routing protocol is required. Timing ing multiple geographically distributed quantum
and synchronization need to be carefully designed. farms. One of the key challenges is the heterogeneity
Network functionalities that are unavailable in clas- among different quantum farms, which may be oper-
sical networks must be designed and implemented. ated by different companies. This requires significant
For instance, quantum decoherence must be care- efforts in terms of network standardization. Further-
fully accounted for within the network design so more, the heterogeneity among quantum links, for
that it can be used to represent a key metric for the example, optical, free space, or satellite, will arise.
network functionalities. Local operations among The delays induced by the distances will introduce
qubits within a single processor must be comple- severe challenges on the entanglement generation
mented by remote operations—operations among and distribution. The increasing number of quantum
qubits placed at different processors. The tradeoff devices to be wired and the heterogeneity of the
between qubits devoted to computation and entan- environments hosting the quantum computers must
gled qubits devoted to communication represents be taken into account.
a key issue with no counterpart in the classical One of the judicious questions raised from this
network design. The very concept of distributed discussion is when will we see the Quantum Inter-
quantum algorithm design must explicitly take such net? There is no definite answer to this question.
a tradeoff and the delay induced by remote opera- However, we firmly believe this is a goal that requires
tions into consideration. a collaborative effort and a multidisciplinary
18 ComputingEdge September 2021You can also read
