Updated December 7, 2021
Defense Primer: Quantum Technology
Quantum technology translates the principles of quantum
militaries to continue to operate at full performance in GPS-
physics into technological applications. In general, quantum
degraded or GPS-denied environments.
technology has not yet reached maturity; however, it could
In addition, quantum sensors could potentially be used in an
hold significant implications for the future of military
intelligence, surveillance, and reconnaissance (ISR) role.
sensing, encryption, and communications, as well as for
Successful development and deployment of such sensors
congressional oversight, authorizations, and appropriations.
could lead to significant improvements in submarine
Key Concepts in Quantum Technology
detection and, in turn, compromise the survivability of sea-
based nuclear deterrents. Quantum sensors could also
Quantum applications rely on a number of key concepts,
enable military personnel to detect underground structures
including superposition, quantum bits (qubits), and
or nuclear materials due to their expected “extreme
entanglement. Superposition refers to the ability of quantum
sensitivity to environmental disturbances.” The sensitivity
systems to exist in two or more states simultaneously. A
of quantum sensors could similarly potentially enable
qubit is a computing unit that leverages the principle of
militaries to detect electromagnetic emissions, thus
superposition to encode information. (A classical computer
enhancing electronic warfare capabilities and potentially
encodes information in bits that can represent binary states
assisting in locating concealed adversary forces.
of either 0 or 1, whereas a quantum computer encodes
information in qubits, each of which can represent 0, 1, or a
Quantum Computers
combination of 0 and 1 at the same time. Thus, the power of
According to NAS, “quantum computers are the only
a quantum computer increases exponentially with the
known model for computing that could offer exponential
addition of each qubit.)
speedup over today’s computers.” While quantum
Entanglement is defined by the National Academy of
computers are in a relatively early stage of development,
Sciences (NAS) as a property in which “two or more
advances—many of which are driven by the commercial
quantum objects in a system can be intrinsically linked such
sector—could hold implications for the future of artificial
that measurement of one dictates the possible measurement
intelligence (AI), encryption, and other disciplines.
outcomes for another, regardless of how far apart the two
objects are.”
For example, some analysts have suggested that quantum
Entanglement underpins a number of potential
computers could enable advances in machine learning, a
military applications of quantum technology. Both
subfield of AI. Such advances could spur improved pattern
superposition and entanglement are, however, difficult to
recognition and machine-based target identification. This
sustain due to the fragility of quantum states, which can be
could in turn enable the development of more accurate
disrupted by minute movements, changes in temperature, or
lethal autonomous weapon systems, or weapons capable of
other environmental factors.
selecting and engaging targets without the need for manual
Military Applications of
human control or remote operation. AI-enabled quantum
Quantum Technology
computers potentially could be paired with quantum sensors
to further enhance military ISR applications.
The Defense Science Board (DSB), an independent
Department of Defense (DOD) board of scientific advisors,
In addition, quantum computers could potentially decrypt
has concluded that three applications of quantum
classified or controlled unclassified information stored on
technology hold the most promise for DOD: quantum
encrypted media, allowing adversaries to gain access to
sensing, quantum computers, and quantum
sensitive information about U.S. military or intelligence
communications. The DSB concluded that quantum radar,
operations. Some analysts note that significant advances in
hypothesized to be capable of identifying the performance
quantum computing would likely be required to break
characteristics (e.g., radar cross-section, speed) of objects—
current encryption methods. Their estimates suggest that a
including low observable, or stealth, aircraft—“will not
quantum computer with around 20 million qubits would be
provide upgraded capability to DOD.”
required to break current encryption methods; however, the
most advanced quantum computers today generally have no
Quantum Sensing
more than 256 qubits.
Quantum sensing uses the principles of quantum physics
within a sensor. According to the DSB, this is the most
The practical applications of quantum computers will likely
mature military application of quantum technologies and is
be realized only after improvement in error rates and
currently “poised for mission use.” Quantum sensing could
development of new quantum algorithms, software tools,
provide a number of enhanced military capabilities. For
and hardware. While, as NAS notes, “there is no guarantee
example, it could provide alternative positioning,
that [these technical challenges] will be overcome,” some
navigation, and timing options that could in theory allow
analysts believe that an initial quantum computer prototype
capable of breaking current encryption methods could be
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Defense Primer: Quantum Technology
developed in the 2030 to 2040 timeframe. For this reason,
potentially address within the next one to three years. It also
NAS concludes that “the development, standardization, and
directs the services to establish programs with small and
deployment of post-quantum cryptography is critical for
medium businesses to provide quantum computing
minimizing the chance of a potential security and privacy
capabilities to government, industry, and academic
disaster.” (Information intercepted prior to the deployment
researchers working on these challenges. Section 1722
of post-quantum cryptography would not be protected.)
directs DOD to conduct an assessment of the risks posed by
quantum computers, as well as current standards for post-
Quantum Communications
quantum cryptography.
Quantum communications—excluding quantum key
DOD did not provide a breakdown of quantum research in
distribution ([QKD], discussed below)—are in a nascent
its FY2021 or FY2022 budget requests; however, according
stage of development. Quantum communications could
to data analytics firm Govini, DOD requested
theoretically enable the secure networking of quantum
approximately $688M for quantum technologies and
military sensors, computers, and other systems, thus
research in FY2021.
improving performance over that of a single quantum
system or classical communications network. Networking
Potential Questions for Congress
could additionally strengthen the robustness of such
What funding level does the current maturity of military
systems at range, thus expanding the potential environments
applications of quantum technology warrant? To what
in which they could be deployed (i.e., outside of the
extent, if at all, should the U.S. government invest in
laboratory settings generally required to sustain fragile
and research technologies that enable quantum military
quantum states). This could significantly expand the
applications (e.g., materials science, fabrication
military utility of quantum communications.
techniques)?
Quantum key distribution is a subset of quantum
To what extent, if at all, can commercial advances in
communications that uses the principles of quantum physics
quantum technology be leveraged for military
to encrypt information that is then sent over classical
applications?
networks. QKD enables secure communications that cannot
be covertly intercepted during transmission. (QKD
How mature are U.S. competitor efforts to develop
communications can, however, be intercepted at the relay
military applications of quantum technologies? To what
stations currently required for long-distance transmissions.)
extent, if at all, could such efforts threaten advanced
China is reportedly investing heavily in QKD and
U.S. military capabilities, such as submarines and
completed construction of an approximately 1,250 mile
stealth aircraft?
Beijing-Shanghai quantum network in 2016. Nonetheless,
What measures are being taken to develop quantum-
the DSB concluded that “QKD has not been implemented
resistant encryption and to protect data that have been
with sufficient capability or security to be deployed for
DOD mission use.”
encrypted using current methods?
What measures, if any, should the United States take to
Funding and Recent Legislative Activity
ensure that the quantum workforce is sufficient to
Congress has considered the management and implications
support U.S. competitiveness in quantum technology?
of quantum technology. For example, Section 234 of the
FY2019 National Defense Authorization Act (NDAA) (P.L.
Related CRS Products
115-232) directs the Secretary of Defense—acting through
CRS Report R45409, Quantum Information Science: Applications,
the Under Secretary of Defense for Research and
Global Research and Development, and Policy Considerations, by
Engineering—to execute a quantum technology research
Patricia Moloney Figliola.
and development program in coordination with the private
sector and other government agencies.
CRS In Focus IF11524, Quantum Information Science:
Congressional Activity and Federal Policy Recommendations, by
Furthermore, Section 220 of the FY2020 NDAA (P.L. 116-
Patricia Moloney Figliola.
92) requires DOD to develop ethics guidelines for the use
CRS Report R46458, Emerging Military Technologies: Background
of quantum technologies, as well as plans for supporting the
and Issues for Congress, by Kelley M. Sayler.
quantum workforce and reducing the cybersecurity risks
associated with quantum technologies. It additionally
authorizes the Secretary of each military department to
Other Resources
establish Quantum Information Science (QIS) Research
Defense Science Board, Applications of Quantum Technologies:
Centers that may “engage with appropriate public and
Executive Summary, October 2019.
private sector organizations” to advance quantum research.
Emily Grumbling and Mark Horowitz, eds., Quantum
To date, the Navy has designated the Naval Research
Computing: Progress and Prospects, National Academy of
Laboratory as its QIS Research Center, while the Air Force
Sciences, 2019.
has designated the Air Force Research Laboratory as a QIS
Research Center for both the Air Force and Space Force.
The Army says it does not plan to establish a QIS Research
Center at this time.
Kelley M. Sayler, Analyst in Advanced Technology and
Section 214 of the FY2021 NDAA (P.L. 116-283) directs
Global Security
the services to compile and annually update a list of
IF11836
technical challenges that quantum computers could
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Defense Primer: Quantum Technology
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