Dec. 4, 2018


New Cryptography Must Be Developed and Deployed Now, Even Though A Quantum Computer That Could Compromise Today’s Cryptography Is Likely At Least A Decade Away, Says New Report
Report Details Risks and Benefits of Developing a Practical Quantum Computer, Identifies Metrics for Tracking Progress

WASHINGTON – Given the current state of quantum computing and the significant challenges that still need to be overcome, it is highly unlikely that a quantum computer that can compromise public-key cryptography – a basis for the security of most of today’s computers and networks – will be built within the next decade, says a new report by the National Academies of Sciences, Engineering, and Medicine.  However, because replacing an established internet protocol generally takes over a decade, work to develop and deploy algorithms that are resilient against an attack by a quantum computer is critical now.

The committee that conducted the study and wrote the report was charged to explore the area of quantum computing and bring clarity about the current state of the art, likely progress toward a general-purpose quantum computer, and the ramifications of its development.

While defeating currently deployed public-key encryption using the best available conventional computer is effectively impossible, a quantum computer could potentially perform this task in no more than a few hours. Even if a sufficiently advanced quantum computer does not arrive within the next thirty years, the report emphasized the need to begin transitioning to quantum resilient procedures to prepare for an attack by such a system, as it takes over a decade to replace existing web standards.

The report describes how a quantum computer operates, describing both the advantages and constraints of this type of computing.  It points out that quantum computers cannot improve all computing and require today’s computing technologies to operate, so quantum computers are unlikely to replace current computers. Rather, they are more likely to be used as accelerators attached to more conventional computers. 

A quantum computer utilizes the unusual characteristics of quantum mechanics –the nonintuitive behavior of very small particles – to perform computation, unlike current computers.  At any given point, a quantum computer, which encodes information as quantum bits or qubits, can span all possible states of a comparable classical computer. This great ability to be in many places at the same time comes with a number of constraints: the qubits need to be intrinsically interconnected, or entangled, isolated from the outside environment, very precisely controlled, and not measured.  These constraints limit the type of tasks a quantum computer can accelerate, and even these cases require careful quantum algorithm design.

Though the arrival of a general-purpose quantum computer would have a major detrimental impact on cryptography, there are many potential benefits of pursuing progress in the field.  Results from research in this space have already helped advance progress in physics, for example, in areas such as quantum gravity, and in computer science by motivating or informing improvements in classical algorithms. Quantum computing, like few other foundational research areas, has the potential to greatly speed up computing for certain applications, which makes supporting a robust research community in the U.S. of strategic value, the report says.

“There has been remarkable progress in the field of quantum computing, and the committee doesn’t see a fundamental reason why a large, functional quantum computer could not be built in principle,” said Mark Horowitz, Yahoo! Founders Professor at Stanford University and chair of the committee. “However, many technical challenges remain to be resolved before we reach this milestone.”

The report identifies significant challenges that lie ahead in the areas of building new algorithms, software, control technologies, and hardware concepts. One of the challenges is the need to correct the errors in a quantum system, without which it is unlikely that a highly complex quantum program would ever run correctly on the system.  However, these algorithms incur significant costs, so in the near term quantum computers are likely to be error-prone, the report said. 

Another significant challenge pointed out by the committee is that while a quantum computer can use a small number of qubits to represent a large amount of data, there is currently no rapid method to convert a large amount of classical data into a quantum state.  Unless a new method is developed for efficiently transferring the data to a quantum computer, the process could reduce or minimize the speedup that is possible overall for a quantum computation on a large dataset.

One of the key findings in the report is that it is still too early to be able to predict the time horizon for a practical quantum computer.  The committee identified several approaches for monitoring progress in the near term and long term, including metrics and milestones.  The report also found that research and development into practical commercial applications of near-term quantum computers-- expected to be much smaller and more error-prone than those that could  defeat public-key encryption – is critical for the field.  The results of this work will have a profound impact on the rate of development of large-scale quantum computers and on the size and robustness of the commercial market.

Additionally, the current research on quantum computing has clear implications for national security, the report said. Any entity that has a large-scale quantum computer could break today’s cryptography to read intercepted communications or stored data.  While the U.S. has historically played a leading role in developing quantum technologies, quantum information science and technology is now a global field, and many other nations have made large resource commitments, the report says. Continued support from the U.S. to this field is imperative if the country wants to maintain its leadership position. 

The study was sponsored by the Office of Director of National Intelligence.  The National Academies of Sciences, Engineering, and Medicine are private, nonprofit institutions that provide independent, objective analysis and advice to the nation to solve complex problems and inform public policy decisions related to science, technology, and medicine.  The National Academies operate under an 1863 congressional charter to the National Academy of Sciences, signed by President Lincoln.  For more information, visit  A committee roster follows.

Riya Anandwala, Media Relations Officer
Andrew Robinson, Media Assistant
Office of News and Public Information
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Copies of Quantum Computing: Progress and Prospects are available from the National Academies Press at or by calling 202-334-3313 or 1-800-624-6242.  Reporters may obtain a copy from the Office of News and Public Information (contacts listed above). 


Division on Engineering and Physical Sciences
Computer Science and Telecommunications Board
Intelligence Community Studies Board

Committee on Technical Assessment of the Feasibility and Implications of Quantum Computing

Mark A. Horowitz1 (chair)
Yahoo! Founders Professor
Stanford University
Stanford, Calif.

Alán Aspuru-Guzik
Canada 150 Research Chair in Quantum Chemistry, and
Professor of Chemistry and Computer Science
University of Toronto

David D. Awschalom1,2
Liew Family Professor in Spintronics and Quantum Information, and
Deputy Director
Institute for Molecular Engineering
University of Chicago

Bob Blakley
Global Director of Information Security Innovation
CitiGroup Inc.
San Antonio

Dan Boneh1
Professor of Computer Science, and
Head of the Applied Cryptography Group
Stanford University
Stanford, Calif.

Susan N. Coppersmith2
Robert E. Fassnacht and Vilas Research Professor of Physics
University of Wisconsin

Jungsang Kim
Department of Electrical and Computer Engineering, and
Department of Physics, and
Department of Computer Science
Duke University
Durham, N.C.

John M. Martinis
Research Scientist
Google, and
Professor of Physics
University of California
Santa Barbara

Margaret Martonosi
Hugh Trumbull Adams ’35 Professor of Computer Science, and
Keller Center for Innovation in Engineering Education
Princeton University
Princeton, N.J.

Michele Mosca
Institute for Quantum Computing, and
Department of Combinatorics & Optimization
Faculty of Mathematics
University of Waterloo
Waterloo, Ontario

William D. Oliver
Laboratory Fellow
Lincoln Laboratory, and
Professor of the Practice
Physics Department, and
Associate Director
Research Laboratory of Electronics
Massachusetts Institute of Technology

Krysta M. Svore
Principal Research Manager
Quantum Architectures and Computation Group
Microsoft Research
Redmond, Wash.

Umesh Virkumar Vazirani2
Roger A. Strauch Professor of Electrical Engineering and Computer Science
University of California


Emily Grumbling
Staff Officer

1Member, National Academy of Engineering
2Member, National Academy of Sciences