Unconditional security of coherent-state-based differential phase shift quantum key distribution protocol with block-wise phase randomization

Hacking on decoy-state quantum key distribution system with partial phase randomization

Quantum key distribution (QKD) provides means for unconditional secure key transmission between two distant parties. However, in practical implementations, it suffers from quantum hacking due to device imperfections. Here we propose a hybrid measurement attack, with only linear optics, homodyne detection, and single photon detection, to the widely used vacuum+weak decoy state QKD system when the phase of source is partially randomized. Our analysis shows that, in some parameter regimes, the proposed attack would result in an entanglement breaking channel but still be able to trick the legitima…

固定频率transmon量子比特中的快速无条件重置与泄漏抑制

Fast unconditional reset and leakage reduction in fixed-frequency transmon qubits

针对容错量子计算中QEC对量子比特重置与泄漏抑制的需求，提出基于可调耦合器的固定频率transmon量子比特快速无条件重置方案，83ns完成全流程且保真度超99%，可缩短QEC周期、提升算法保真度。

对抗浅层量子电路的无条件伪随机性

Unconditional Pseudorandomness against Shallow Quantum Circuits

针对QNC^0等浅层量子电路，本文利用量子态2-设计、随机相位子空间态和酉2-设计，给出无需复杂性假设的高效伪随机态、伪纠缠态与并行查询伪随机酉构造。

Randomized ancillary qubit overcomes detector-control and intercept-resend hacking of quantum key distribution

Practical implementations of quantum key distribution (QKD) have been shown to be subject to various detector side-channel attacks that compromise the promised unconditional security. Most notable is a general class of attacks adopting the use of faked-state photons as in the detector-control and, more broadly, the intercept-resend attacks. In this paper, we present a simple scheme to overcome such class of attacks: A legitimate user, Bob, uses a polarization randomizer at his gateway to distort an ancillary polarization of a phase-encoded photon in a bidirectional QKD configuration. Passing t…

Practical post-processing for quantum-key-distribution experiments

Quantum key distribution (QKD) promises unconditionally secure key generation between two distant parties by wisely exploiting properties of quantum mechanics. In QKD, experimental measurements on quantum states are transformed to a secret key and this has to be done in accordance with a security proof. Unfortunately, many theoretical proofs are not readily implementable in experiments and do not consider all practical issues. Therefore, in order to bridge this "practical gap", we integrate a few existing theoretical results together with new developments, in effect producing a simple and comp…