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