Physical implementations of cryptographic algorithms leak information, which makes them vulnerable to so-called side-channel attacks. The problem of secure computation in the presence of leakage is generally known as leakage resilience. In this work, we establish a connection between leakage resilience and fault-tolerant quantum computation. We first prove that for a general leakage model, there exists a corresponding noise model in which fault tolerance implies leakage resilience. Then we show how to use constructions for fault-tolerant quantum computation to implement classical circuits that are secure in specific leakage models.
As we are entering the era of constructing practical quantum computers, suppressing the inevitable noise to accomplish reliable computational tasks will be the primary goal. Leakage noise, as the amplitude population leaking outside the qubit subspace, is a particularly damaging source of error that error correction approaches cannot handle. However, the impact of this noise on the performance of variational quantum algorithms (VQAs), a type of near-term quantum algorithms that is naturally resistant to a variety of noises, is yet unknown. Here, {we consider a typical scenario with the widely …
We introduce the notion of fault-tolerant quantum metrology to overcome noise beyond our control -- associated with sensing the parameter, by reducing the noise in operations under our control -- associated with preparing and measuring probes and ancillae. To that end, we introduce noise thresholds to quantify the noise resilience of parameter estimation schemes. We demonstrate improved noise thresholds over the non-fault-tolerant schemes. We use quantum Reed-Muller codes to retrieve more information about a single phase parameter being estimated in the presence of full-rank Pauli noise. Using…
Quantum data locking is a quantum communication primitive that allows the use of a short secret key to encrypt a much longer message. It guarantees information-theoretical security against an adversary with limited quantum memory. Here we present a quantum data locking protocol that employs pseudo-random circuits consisting of Clifford gates only, which are much easier to implement fault tolerantly than universal gates. We show that information can be encrypted into $n$-qubit code words using order $n - H_\mathrm{min}(\mathsf{X})$ secret bits, where $H_\mathrm{min}(\mathsf{X})$ is the min-entr…
Leakage Suppression in Quantum Control via Static Parameter Offsets
Key Laboratory of Atomic and Subatomic Structure and Quantum Control (Ministry of Education), Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter, and School of Physics, South China Normal University（原子与亚原子结构及量子控制重点实验室（教育部），广东省物质结构与基本相互作用卓越研究中心，华南师范大学物理学院）；Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, Guangdong-Hong Kong Joint Laboratory of Quantum Matter, and Frontier Research Institute for Physics, South China Normal University（广东省量子工程与量子材料重点实验室，广东-香港量子物质联合实验室，华南师范大学前沿物理研究院）
Impact of leakage on the dynamics of a ST$_0$ qubit implemented in a Double Quantum Dot device
Tecnun - University of Navarra（塔库纳-纳瓦拉大学）；Donostia International Physics Center（圣塞巴斯蒂安国际物理中心）；Cavendish Laboratory, Department of Physics, University of Cambridge（剑桥大学物理系卡文迪许实验室）；Hitachi Cambridge Laboratory（日立剑桥实验室）
We consider a continuous-variable (CV) quantum key distribution (QKD) protocol over free-space channels, which is simpler and more robust than typical CV QKD protocols. It uses a bright laser, squeezed and modulated in the amplitude quadrature, and self-homodyne detection. We consider a scenario, where the line of sight is classically monitored to detect active eavesdroppers, so that we can assume a passive eavesdropper. Under this assumption, we analyse security of the QKD protocol in the composable finite-size regime. Proper modulation of the squeezed laser to the shot-noise level can comple…
Two fault tolerant authenticated quantum dialogue (AQD) protocols are proposed in this paper by employing logical Bell states as the quantum resource, which combat the collective-dephasing noise and the collective-rotation noise, respectively. The two proposed protocols each can accomplish the mutual identity authentication and the dialogue between two participants simultaneously and securely over one kind of collective noise channels. In each of two proposed protocols, the information transmitted through the classical channel is assumed to be eavesdroppable and modifiable. The key for choosin…
Non-Abelian geometric phases acquired in cyclic quantum evolution can be utilized as natural resources for constructing robust holonomic gates for quantum information processing. Recently, an extensible holonomic quantum computation (HQC) was proposed and demonstrated in a recent superconducting experiment [T. Yan et al., Phys. Rev. Lett. 122, 080501 (2019)]. However, for the weakly anharmonic system, this HQC was given of low gate fidelity due to leakage to states outside of the computational subspace. Here, we propose a scheme that to construct nonadiabatic holonomic gates via dynamical inva…
量子码擅长纠正局部噪声，但无法纠正将量子位激发到计算空间之外的状态的泄漏故障。Aliferis和Terhal已经证明，使用称为泄漏减少单元（LRU）的小工具，泄漏故障存在一个准确度阈值。然而，这些小工具降低了准确性阈值，并可能增加开销和实验复杂性，这些成本尚未得到彻底理解。我们的工作探讨了各种技术的泄漏弹性，容错纠错的拓扑代码的上下文中。我们的贡献是三方面的。首先，我们开发了一个泄漏模型，从早期的模型不同的关键细节。其次，我们使用蒙特卡罗模拟来检视几个伴随式撷取电路。第三，考虑到执行三个结果测量的能力，我们提出了一个显着改进的综合征处理算法。我们的模拟结果表明，当泄漏和去极化噪声率相当时，每个量子比特有一个额外的CNOT并且没有额外的辅助元件的简单电路将精度阈值降低了不到4倍。当解码器使用3-结果测量时，这变为因子2。最后，当物理错误率小于2 x 10^-4时，在每个门之后放置LRU可以实现我们考虑的所有电路中最低的逻辑错误率。我们希望密切相关的平面和旋转码表现出相同的精度阈值，这些想法可以自然地推广到其他拓扑码。
Plugging Leaks in Fault-Tolerant Quantum Computation and Verification
National Quantum Computing Centre, Rutherford Appleton Laboratory（拉瑟福德·阿普尔顿实验室国家量子计算中心）；School of Informatics, University of Edinburgh（爱丁堡大学信息学院）；Quandela；Département d’Informatique, Ecole Normale Supérieure（巴黎高等师范学院计算机科学系）
Quantum holonomic gates hold built-in resilience to local noises and provide a promising approach for implementing fault-tolerant quantum computation. We propose to realize high-fidelity holonomic $(N+1)$-qubit controlled gates using Rydberg atoms confined in optical arrays or superconducting circuits. We identify the scheme, deduce the effective multi-body Hamiltonian, and determine the working condition of the multiqubit gate. Uniquely, the multiqubit gate is immune to systematic errors, i.e., laser parameter fluctuations and motional dephasing, as the $N$ control atoms largely remain in the…
In this paper, two fault tolerant channel-encrypting quantum dialogue (QD) protocols against collective noise are presented. One is against collective-dephasing noise, while the other is against collective-rotation noise. The decoherent-free states, each of which is composed of two physical qubits, act as traveling states combating collective noise. Einstein-Podolsky-Rosen pairs, which play the role of private quantum key, are securely shared between two participants over a collective-noise channel in advance. Through encryption and decryption with private quantum key, the initial state of eac…
Spectator Leakage Suppression via Invariant Subspace Engineering for CZ Gates in Superconducting Quantum Circuits
University of Science and Technology of China（中国科学技术大学）；CAS Center For Excellence in Quantum Information and Quantum Physics（中国科学院量子信息与量子物理前沿卓越创新中心）；Suzhou Institute for Advanced Research, University of Science and Technology of China（中国科学技术大学苏州高等研究院）；Institute of Artificial Intelligence, Hefei Comprehensive National Science Center（合肥综合性国家科学中心人工智能研究院）
We propose a scheme for fault-tolerant long-range entanglement generation at the ends of a rectangular array of qubits of length $R$ and a square cross section of size $d\times d$ with $d=O(\log R)$. Up to an efficiently computable Pauli correction, the scheme generates a maximally entangled state of two qubits using a depth-$6$ circuit consisting of nearest-neighbor Clifford gates and local measurements only. Compared with existing fault-tolerance schemes for quantum communication, the protocol is distinguished by its low latency: starting from a product state, the entangled state is prepared…
Stabilized cat codes can provide a biased noise channel with a set of bias-preserving (BP) gates, which can significantly reduce the resource overhead for fault-tolerant quantum computing. All existing schemes of BP gates, however, require adiabatic quantum evolution, with performance limited by excitation loss and non-adiabatic errors during the adiabatic gates. In this work, we apply a derivative-based leakage suppression technique to overcome non-adiabatic errors, so that we can implement fast BP gates on Kerr-cat qubits with improved gate fidelity while maintaining high noise bias. When ap…
Engineering dissipation and control pulses for high-fidelity fault-tolerance quantum computing
Fujian Key Laboratory of Quantum Information and Quantum Optics, Fuzhou University（福州大学）；Department of Physics, Fuzhou University（福州大学）；Quantum Information Physics Theory Research Team, Center for Quantum Computing, RIKEN（理化学研究所）；Institute of Quantum Science and Technology, Yanbian University（延边大学）
Local Clustering Decoder as a fast and adaptive hardware decoder for the surface code
Riverlane；Quantum Engineering Technology Labs, H. H. Wills Physics Laboratory and Department of Electrical & Electronic Engineering, University of Bristol（布里斯托大学电气与电子工程系、H.H.威尔斯物理实验室量子工程技术实验室）
Taming Rydberg Decay with Measurement-based Quantum Computation
Hefei National Research Center for Physical Sciences at the Microscale and School of Physical Sciences, University of Science and Technology of China（中国科学技术大学物理科学学院和微观尺度物理国家研究中心）；Shanghai Research Center for Quantum Science and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China（中国科学技术大学上海量子科学研究中心和中科院量子信息重点实验室）；Hefei National Laboratory, University of Science and Technology of China（中国科学技术大学合肥国家实验室）
Photon-Number Conserved Universal Quantum Logic Employing Continuous-Time Quantum Walk on Dual-Rail Qubit Arrays
Southern University of Science and Technology（南方科技大学）；Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology（南方科技大学量子科学工程学院）；Lanzhou University（兰州大学）；Cuiying Honors College, Lanzhou University（兰州大学萃英学院）；International Quantum Academy, Shenzhen（深圳国际量子研究院）
To solve classically hard problems, quantum computers need to be resilient to the influence of noise and decoherence. In such a fault-tolerant quantum computer, noise-induced errors must be detected and corrected in real-time to prevent them from propagating between components. This requirement is especially pertinent while applying quantum gates, when the interaction between components can cause errors to quickly spread throughout the system. However, the large overhead involved in most fault-tolerant architectures makes implementing these systems a daunting task, which motivates the search f…
Geometric phase is an indispensable element for achieving robust and high-fidelity quantum gates due to its built-in noise-resilience feature. However, due to the complexity of manipulation and the intrinsic leakage of the encoded quantum information to non-logical-qubit basis, the experimental realization of universal nonadiabatic holonomic quantum computation is very difficult. Here, we propose to implement scalable nonadiabatic holonomic quantum computation with decoherence-free subspace encoding on a two-dimensional square superconducting transmon-qubit lattice, where only the two-body int…
The key for realizing fault-tolerant quantum computation lies in maintaining the coherence of all qubits so that high-fidelity and robust quantum manipulations on them can be achieved. One of the promising approaches is to use geometric phases in the construction of universal quantum gates, due to their intrinsic robustness against certain types of local noises. However, due to limitations in previous implementations, the noise-resilience feature of nonadiabatic holonomic quantum computation (NHQC) still needs to be improved. Here, combining with the dynamical correction technique, we propose …
Fault-tolerant hyper-Ramsey spectroscopy of optical clock transitions with dynamical decoupling
Centre for Quantum Technologies, Department of Physics, Sofia University（索非亚大学量子技术中心物理系）；Sorbonne Université CNRS, MONARIS, UMR 8233（索邦大学CNRS，MONARIS实验室）；MajuLab, International Research Laboratory IRL 3654, Université Côte d’Azur, Sorbonne Université, National University of Singapore, Nanyang Technological University（新加坡国立大学-索邦大学-尼斯蔚蓝海岸大学南洋理工大学联合研究实验室）；Center for Quantum Technologies, Nanyang Technological University（南洋理工大学量子技术中心）；Nanyang Quantum Hub, School of Physical and Mathematical Sciences, Nanyang Technological University（南洋理工大学理学院南洋量子枢纽）；Laboratoire de Physique des Lasers, CNRS, Université Sorbonne Paris Nord（巴黎北索邦大学CNRS激光物理实验室）
A central claim in quantum cryptography is that secrecy can be proved rigorously, based on the assumption that the relevant information-processing systems obey the laws of quantum physics. This claim has recently been challenged by Bernstein (arXiv:1803.04520). He argues that the laws of physics may also entail an unavoidable leakage of any classical information encoded in physical carriers. The security claim of quantum key distribution would then be vacuous, as the computation of the final secret key would leak its value. However, as we explain in this short note, Bernstein's reasoning is ba…
