Open research questions in Quantum Information and Cryptography
279 unresolved questions extracted from the limitations and future-work sections of 774 Quantum Information and Cryptography papers in our library. Each links back to the study that raised it.
What the literature leaves open
The matching converse leverages the superdense coding bound (which, without the integer-qudit restriction, still gives a universal lower bound of half the classical bandwidth; closing the residual odd-α gap is Open Question 1 below). 2k log Open questions include: (1) closing the gap between ⌈α/2⌉ log 2 q per helper for odd α (non-integer qudit dimensions); (2) characterizing the entanglement-bandwidth trade-off when helpers share less-than-maximal entanglement; (3) the bandwidth-vs-helpers tradeoff for du > k: with more helpers participating, the per-helper requirement weakens, but it is unclear whether the total bandwidth can drop below ⌈α/2⌉k log 2 q; (4) the update bandwidth for non-MDS codes.
Quantum Entanglement Halves the Oblivious Update Bandwidth · 2026Future work includes experimental validation on entangled atomic sensor networks such as the Malia et al. platform [10], extension to adaptive entangle- ment distribution based on real-time decoherence monitoring using the Data-Cleaning Tree frame- work [16], integration with the compressed sensing 10 framework [18] for quantum state tomography in large-scale networks, and a full quantum channel analysis replacing the scalar visibility model with Kraus operator representations of physical decoher- ence processes.
Quantum-Enhanced Distributed Sensor Fusion: Lower Bounds on Aggregation from Projection Noise to Heisenberg-Limited Byzantine-Tolerant Networks · 2026Photon loss remains a critical limitation for practical implementation - The study focuses on a specific type of interferometer (hybrid interferometer with a coherent state and a vacuum state as inputs)
Further research on optimizing the beam splitter's transmittance for maximizing phase sensitivity in lossy conditions - Investigating the performance of the proposed scheme in different types of interferometers
The need for custom detectors or output amplifier chains in the dilution refrigerator for full PDH with square-law detection, - The implementation requires generating three input tones and carrying out three digital downconversions
Exploring the use of cryogenic square-law detectors for direct PDH beatnote detection, - Investigating the application of PDH readout to larger-scale quantum computers
The system is limited to a three-node setup, - The study does not demonstrate other types of attacks, such as direct channel wiretapping during the distribution of entangled states, - The study leaves experimental demonstrations of other types of attacks for future work
Experimental demonstrations of other types of attacks, such as direct channel wiretapping during the distribution of entangled states, - Demonstrating more advanced quantum communication protocols, such as multipartite entanglement purification and quantum voting
SQOUT is a prototype and has not undergone formal certification, - SQOUT remains under active development
Existing cybersecurity frameworks do not cover the practical vulnerabilities of quantum communication systems. There is a need for a threat model that addresses these vulnerabilities. There is a need for a risk scoring methodology that is compatible with existing standards.
The squeezed vacuum therefore illustrates why energy alone is insufficient for geometric Landau–Zener interferometry: a state can contain battery energy but fail to define the azimuthal phase of the transverse qubit coupling.
Quantum-Battery-Powered Geometric Landau-Zener Interferometry · 2026Across this set, post-quantum cryptography performance is evaluated only in simulated or laboratory environments (wireless networks, TLS integration, IoT testbeds); none of the studies measure real-world deployment performance, operational costs, or integration challenges in Pakistan's existing telecommunications infrastructure, legacy systems, or resource-constrained government networks.
This interpretation is statistically unjustified because it does not account for the total experimental resources required to construct an estimator.
Comment on J.Qin et al., Unconditional and Robust Quantum Metrological Advantage beyond N00N States, PRL 130, 070801 (2023) and J.A. H. Nielsen et.al., Deterministic Quantum Phase Estimation beyond N00N States. PRL 130, 123603 (2023) · 2026In a realistic scenario where the generation rate is limited by the two-way communication time, we show that up to 15 % of the $393 μs$ round-trip communication time is filled with communication trials, leading to a 60-fold enhancement in the rate of detected telecom photons correlated with the quantum memory array, compared to a single-mode memory.
Distribution of light-matter quantum correlations with a temporally multiplexed solid-state quantum memory array · 2026It is often particularly important that local parameters remain unknown and that only the global function is shared across the network.
Experimental Private Quantum Networked Sensing · 2026Abstract Authentication is a fundamental building block of secure quantum networks, essential for quantum cryptographic protocols and often debated as a key limitation of quantum key distribution (QKD) in security standards.
However, its security against source-side light-injection attacks remains unexplored.
Unidimensional-modulation Continuous-variable Quantum Key Distribution under Light-injection Attacks · 2026 · DOIHowever, the underlying mechanism of the QME in the presence of long-range interactions remains unclear.
Quantum networks (QNs) exhibit stronger connectivity than predicted by classical percolation, yet the origin of this phenomenon remains unexplored.
Typically, this increases the quantum Fisher information with respect to changes in system parameters and thus improves the optimally possible measurement precision limited by the Cramér-Rao bound.
However, the entanglement spectrum remains insufficiently explored for topological states without a bulk energy gap.
Universal Entanglement Spectrum in One-Dimensional Gapless Symmetry Protected Topological States · 2024 · DOIHowever, this enhancement is usually limited to a very narrow region around the critical point.
The application of this property beyond proof-of-principle in quantum physics, is an open question.
More than confirming the efficacy of our gate scheme, this high-fidelity result also reveals a promising but rarely explored parameter space uniquely suitable for gate operations between fluxonium qubits.
It can be applied to semi-device-independent scenarios also, where the measurement devices and network nodes are not well characterized and trusted.
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
- Twin-field quantum key distribution over 830-km fibre · Nature Photonics · 2022 · 523 citations
- The Evolution of Quantum Key Distribution Networks: On the Road to the Qinternet · IEEE Communications Surveys & Tutorials · 2022 · 494 citations
- Experimental Twin-Field Quantum Key Distribution over 1000 km Fiber Distance · Physical Review Letters · 2023 · 372 citations
- Entangled quantum systems and the Schmidt decomposition · American Journal of Physics · 1995 · 371 citations
Most recent work
- Device-independent quantum key distribution over 100 km with single atoms · Science · 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
- Preparation of conditionally squeezed states in qubit-oscillator systems · Physical Review Research · 2026
- Logical entanglement distribution between distant two-dimensional array qubits · Physical Review Research · 2026
- Universal resources for quantum approximate optimization algorithm and quantum annealing · Physical Review Research · 2026
- Attosecond quantum optical interferometry · Reports on Progress in Physics · 2026
- Analytical phase boundary of a quantum driven-dissipative Kerr oscillator from classical stochastic instantons · Physical Review Research · 2026
- Blueprint for experiments exploring the quantum recurrence theorem on a coupled multiqubit system · Physical Review Research · 2026
- Scalable entangling gates on ion qubits via structured light addressing · Science Advances · 2026
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