Open research questions in Quantum Information and Cryptography
618 gap statements mined from Quantum Information and Cryptography papers in our 7.9M-paper local library, which holds 4,426 papers on the topic — drawn mostly from each paper's own stated research gap, future-work, challenge and limitation notes, and its abstract. The ones listed below are a selection still marked open; each names the study that raised it, with a DOI link where the paper has one.
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What the literature leaves open
To address the four core challenges facing resource-constrained edge devices in the deployment of quantum-resistant security—namely device heterogeneity, resource limitations, protocol incompatibility, and high engineering costs—this work establishes a synergistic, lightweight mitigation framework.
Quantum-Resistant Security Technologies for Resource-Constrained Edge Devices: Challenges and Lightweight Countermeasures · 2026 · DOIHigher-dimensional channels are out of reach of the present programs, and whether the observed approach of the NH bound toward the SLD bound continues at larger k is an open question.
Saturating the Bayesian Nagaoka-Hayashi bound within numerical precision for the depolarization SU(2) rotation channel · 2026 · DOIThe frozen discord and residual steering coherence surviving after ESD are genuine nonclassical resources, but they are insufficient to sustain teleportation advantage under this protocol.
The relevant quantities—the detection sensitivity and alarm threshold against auxiliary-light attacks, the reflectivity of the detector connections, the residual injected light reaching the encoding components, and the dynamic range and response of SPAD3 under strong illumination— were not characterized in the present experiment.
Quantum key distribution over a three-user fiber network with passive optical circulator · 2026 · DOIWhile the prior research confirmed dual certificate is uniquely determined via spectral calculus when the error matrix is full-rank, the efficiently verifiable optimality conditions for the rank-deficient (singular) error matrices have remained an open question. Our counterexample shows that the conjectured spectral condition is insufficient to certify the optimality in the general case.
Extending the feasible operating window to support session-key lengths meeting the conventional 128-bit benchmark, establishing a formal proof of one-time indistinguishability, and validating routed implementations on current-generation hardware remain open problems, and the study provides an experimentally grounded characterisation of the protocol’s capabilities and limitations under current NISQ conditions.
The need to generate an ITS initial key without pre-shared secrets. The challenge of achieving a fully ITS-authenticated entanglement-based QKD protocol.
Unconditional authentication in quantum key distribution via hybrid entangled physical unclonable functions · 2026 · DOIThe complexity of the congruence system and the need for a systematic classification. The challenge of extending the parity-based classification known for qubits to arbitrary finite dimensions. The need to derive a closed-form expression for the reduced density matrix.
There is a need for quantum technologies to demonstrate significant advantages across diverse domains. Classical techniques are approaching fundamental limitations, and new methods are required to enhance sensitivity and resolution. The application of squeezed light in quantum sensing is still in its early stages, and further research is needed to realize its potential.
For an external eavesdropper, the classical measurement results announced by the sender and controllers are insufficient by themselves to fully reconstruct the target states, and the target states are not directly transmitted through the channel as independent quantum particles.
Although the complete answer to the above question remains unclear, we show in the next section that another type of hierarchy of extensions, called complete graph extendibility, can be fully characterized in terms of the copositive sum of squares hierarchy, generalizing some results from the literature., entangled bose-symmetric states having high degree of extendibility, remains to be a challenging problem.
The present implementation relies on post-selected linear-optical operations, together with pre-entanglement between the system and ancilla photons, which can open sidechannels for a various set of new attacks; therefore, further work is required for the full verification of security.
Proof-of-Principle Implementation of Quantum Key Distribution in an Indefinite Causal Order · 2026 · DOIThere are some limitations to the presented protocol and security analysis, which can open up areas that can be explored in the future.
While the quantum operations are intended to run in parallel, sequential execution is also possible if quantum resources are insufficient, allowing the participants to be divided into smaller groups for sequential processing.
However, it remains unclear which quantum channels correspond precisely to 0 7 a given block noncommutative graph Σ.
Sufficient conditions for additivity of the zero-error classical capacity of quantum channels · 2026 · DOIGiven the complexity of hardware noise, theory and classical simulation are insufficient to settle this.
Encrypted cloning of qubits is able to serve as a quantum primitive, already on non-error-corrected quantum hardware · 2026 · DOIIt has remained an open question, however, whether encrypted cloning is stable under hardware noise and thus practical as a quantum primitive.
Encrypted cloning of qubits is able to serve as a quantum primitive, already on non-error-corrected quantum hardware · 2026 · DOIRydberg atoms enable ultrasensitive microwave detection through their exceptional polarizability, but their use as decoders in communications is limited by a scarcity of scalable frequency points, which arises from cross-modulation in multifrequency fields and narrow operational bandwidth of the sensor.
The paper suggests future research directions in the construction of QCCC commitment schemes. The paper suggests investigating the relationship between QCCC protocols and classical IEG frameworks.
The paper identifies a need for novel cryptographic primitives to enhance the security of commitment schemes.
When the probe detuning is zero, the possible range of applied powers is severely limited by the onset of added MIST, and significant increases in p(o|g) and p(o|e) are observed at approximately −38 dBm, indicating that heterodyne readout can only be carried out at carrier powers well below this level.
The community is encouraged to utilize and contribute to the open-source SQcircuit project to further enhance the tool's functionality and broaden its application scope.
A General Framework for Gradient-Based Optimization of Superconducting Quantum Circuits using Qubit Discovery as a Case Study · 2026 · DOIExisting methods are not efficient or precise for optimizing superconducting quantum circuits.
A General Framework for Gradient-Based Optimization of Superconducting Quantum Circuits using Qubit Discovery as a Case Study · 2026 · DOIFuture challenges and opportunities in the field are discussed, - Achieving stable squeezing at low frequencies, - Optimization of pump and probe beam…
Further development of AQT as a genuine quantum-tomography-like protocol. Exploration of the applications of attosecond quantum optical interferometry. Investigation of the limitations of AQT.
Most-cited papers in Quantum Information and Cryptography
- Experimental quantum teleportation · Nature · 1997 · 4,749 citations
- Long-distance quantum communication with atomic ensembles and linear optics · Nature · 2001 · 3,239 citations
- Entanglement of the orbital angular momentum states of photons · Nature · 2001 · 3,013 citations
- Quantum-Enhanced Measurements: Beating the Standard Quantum Limit · Science · 2004 · 2,805 citations
- Unconditional Quantum Teleportation · Science · 1998 · 2,655 citations
- Quantum information and computation · Nature · 2000 · 2,211 citations
- Advances in quantum cryptography · Advances in Optics and Photonics · 2020 · 2,055 citations
- Circuit quantum electrodynamics · Reviews of Modern Physics · 2021 · 1,887 citations
- Secure quantum key distribution with realistic devices · Reviews of Modern Physics · 2020 · 1,545 citations
- An integrated space-to-ground quantum communication network over 4,600 kilometres · Nature · 2021 · 1,003 citations
Most recent work
- Symmetric quantum states: a review of recent progress · Reports on Progress in Physics · 2026
- Device-independent quantum key distribution over 100 km with single atoms · Science · 2026
- SFTRAP: Satisfying Fidelity Threshold Routing and Adaptive Purification for Throughput Maximum in Quantum Network · IEEE Transactions on Communications · 2026
- Quantum Internet Architecture: Unlocking Quantum-Native Routing via Quantum Addressing · IEEE Transactions on Communications · 2026
- Quantum Mpemba Effect in Long-Range Spin Systems · Physical Review Letters · 2026
- High-rate quantum key distribution with compact state preparation and detection · Proceedings of the National Academy of Sciences · 2026
- Operational interpretation of the Stabilizer Entropy · Quantum · 2026
- Rydberg Atomic Quantum Receivers for Classical Wireless Communications and Sensing: Their Models and Performance · IEEE Transactions on Communications · 2026
- Adversarial robustness guarantees for quantum classifiers · npj Quantum Information · 2026
- A Novel Quantum-Based Mutual Authentication and Key Agreement Scheme for Smart Grid · IEEE Transactions on Information Forensics and Security · 2026
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