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Pulsed Homodyne Measurement of Multi-Mode Squeezed Vacua for Large Scale quantum Computation

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Pulsed Homodyne Measurement of Multi-Mode Squeezed Vacua for...

CLEO: Fundamental Science, CLEO:FS 2024 - Part of Conference on Lasers and Electro-Optics, CLEO 2024

作者： Nomura, Takefumi Endo, Mamoru Kashiwazaki, Takahiro Umeki, Takeshi Nehra, Rajveer Takase, Kan Asavanant, Warit Furusawa, Akira Department of Applied Physics School of Engineering The University of Tokyo 7-3-1 Hongo Bunkyo Tokyo113-8656 Japan Optical Quantum Computing Research Team RIKEN Center for Quantum Computing 2-1 Hirosawa Saitama Wako351-0198 Japan NTT Device Technology Labs. NTT Corporation 3-1 Morinosato Wakamiya Kanagawa Atsugi243-0198 Japan Department of Electrical and Computer Engineering University of Massachusetts-Amherst AmherstMA01003 United States Department of Physics University of Massachusetts-Amherst AmherstMA01003 United States

Optical quantum computers require a large number of squeezed vacua. In this research, 36 squeezed spectral modes were produced with type-0 lithium niobate waveguide, thus demonstrating its scalability as a resource fo... 详细信息

ISBN: (纸本)9781957171395

关键词： quantum computers

A SPRINT-Based Single Photon Subtractor for PNS Attacks on QKD

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A SPRINT-Based Single Photon Subtractor for PNS Attacks on Q...

Photonics North

作者： Abdolreza Pasharavesh Michal Bajcsy Institute for Quantum Computing University of Waterloo Waterloo ON Canada Electrical and Computer Engineering Department University of Waterloo Waterloo ON Canada

ISBN: (数字)9798350366365

ISBN: (纸本)9798350366372

We present a photon subtraction scheme designed to deterministically extract single photons from multiphoton states within arbitrary input pulses of light using single-photon Raman interaction (SPRINT) [1]. The proposed system comprises two cascaded Lambda-type atoms with transitions selectively coupled to distinct modes of a single chiral waveguide. Through numerical simulations, we evaluate the device's performance in a potential application involving photon-number-splitting (PNS) attacks against quantum key distribution (QKD).

关键词： Waveguide transitions Performance evaluation Atoms Numerical simulation quantum key distribution Photonics

Tolerant quantum Junta Testing

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arXiv 2024年

作者： Chen, Zhaoyang Li, Lvzhou Luo, Jingquan Institute of Quantum Computing and Software School of Computer Science and Engineering Sun Yat-sen University Guangzhou510006 China

Junta testing for Boolean functions has sparked a long line of work over recent decades in theoretical computer science, and recently has also been studied for unitary operators in quantum computing. Tolerant junta testing is more general and challenging than the standard version. While optimal tolerant junta testers have been obtained for Boolean functions, there has been no knowledge about tolerant junta testers for unitary operators, which was thus left as an open problem in [Chen, Nadimpalli, and Yuen, SODA2023]. In this paper, we settle this problem by presenting the first algorithm to decide whether a unitary is ϵ1-close to some quantum k-junta or is ϵ2-far from any quantum k-junta, where an n-qubit unitary U is called a quantum k-junta if it only non-trivially acts on just k of the n qubits. More specifically, we present a tolerant tester with (Equation presented), and ρ ∈ (0, 1), and the query complexity is (Equation presented), which demonstrates a trade-off between the amount of tolerance and the query complexity. Note that our algorithm is non-adaptive which is preferred over its adaptive counterparts, due to its simpler as well as highly parallelizable nature. At the same time, our algorithm does not need access to U†, whereas this is usually required in the literature. © 2024, CC BY.

关键词： Boolean functions

Implementation of Continuous-Time quantum Walk on Sparse Graph

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arXiv 2024年

作者： Chen, Zhaoyang Li, Guanzhong Li, Lvzhou Institute of Quantum Computing and Software School of Computer Science and Engineering Sun Yat-sen University Guangzhou510006 China

Continuous-time quantum walks (CTQWs) play a crucial role in quantum computing, especially for designing quantum algorithms. However, how to efficiently implement CTQWs is a challenging issue. In this paper, we study implementation of CTQWs on sparse graphs, i.e., constructing efficient quantum circuits for implementing the unitary operator e−iHt, where H = γA (γ is a constant and A corresponds to the adjacency matrix of a graph). Our result is, for a d-sparse graph with N vertices and evolution time t, we can approximate e−iHt by a quantum circuit with gate complexity (d3||H||tN log N)1+o(1), compared to the general Pauli decomposition, which scales like (||H||tN4 log N)1+o(1). For sparse graphs, for instance, d = O(1), we obtain a noticeable improvement. Interestingly, our technique is related to graph decomposition. More specifically, we decompose the graph into a union of star graphs, and correspondingly, the Hamiltonian H can be represented as the sum of some Hamiltonians Hj, where each e−iHjt is a CTQW on a star graph which can be implemented efficiently. © 2024, CC BY.

关键词： quantum computers

Super-exponential quantum advantage for finding the center of a sphere

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arXiv 2024年

作者： Li, Guanzhong Li, Lvzhou Institute of Quantum Computing and Software School of Computer Science and Engineering Sun Yat-sen University Guangzhou510006 China

This article considers the geometric problem of finding the center of a sphere in vector space over finite fields, given samples of random points on the sphere. We propose a quantum algorithm based on continuous-time quantum walks that needs only a constant number of samples to find the center. We also prove that any classical algorithm for the same task requires approximately as many samples as the dimension of the vector space, by a reduction to an old and basic algebraic result—Warning’s second theorem. Thus, a super-exponential quantum advantage is revealed for the first time for a natural and intuitive geometric problem. © 2024, CC BY.

关键词： Spheres

Generating Schrodinger's Kitten State From Coherent Pulses via Deterministic Photon Subtraction

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Generating Schrodinger's Kitten State From Coherent Pulses v...

Pacific Rim Conference on Lasers and Electro-Optics (CLEO/Pacific Rim)

作者： Abdolreza Pasharavesh Michal Bajcsy Institute for Quantum Computing University of Waterloo Waterloo ON Canada Department of Electrical and Computer Engineering University of Waterloo Waterloo ON Canada

We propose a scheme to generate Schrodinger's kitten states by subtracting single photons from coherent pulses through single-photon Raman interaction. Our findings suggest fidelities exceeding 99%, offering a pro... 详细信息

ISBN: (数字)9798350372076

ISBN: (纸本)9798350372083

关键词： Electro-optical waveguides Photonics

Circuit Complexity of Sparse quantum State Preparation

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arXiv 2024年

作者： Luo, Jingquan Li, Lvzhou Institute of Quantum Computing and Software School of Computer Science and Engineering Sun Yat-sen University Guangzhou510006 China

quantum state preparation is a fundamental and significant subroutine in quantum computing. In this paper, we conduct a systematic investigation on the circuit size for sparse quantum state preparation. A quantum state is said to be d-sparse if it has only d non-zero amplitudes. For the task of preparing an n-qubit d-sparse quantum state, we obtain the following results: • Without ancillary qubits: We propose the first approach that uses o(dn) elementary gates without using ancillary qubits. Specifically, it is proven that any n-qubit d-sparse quantum state can be prepared by a quantum circuit of size O(logdnn +n) without using ancillary qubits. This is asymptotically optimal when d = poly(n), and this optimality extends to a broader scope under some reasonable assumptions. • With limited ancillary qubits: (i) We show that any n-qubit d-sparse quantum state can be prepared by a quantum circuit of size O(logdnd) and depth Θ(log dn) using at most O(logndd) ancillary qubits, which not only reduces the circuit size compared to the one without ancillary qubits when d = ω(poly(n)), but also achieves the same asymptotically optimal depth while utilizing fewer ancillary qubits and applying fewer quantum gates compared to the result given in [Physical Review Letters, 129, 230504(2022)]. (ii) We establish the lower bound Ω(log(n+dnm)+log d + n) on the circuit size with m ancillary qubits available. Additionally, we demonstrate a slightly stronger lower bound Ω(log(dnn+m) + n) under reasonable assumptions. • With unlimited ancillary qubits: We prove that with arbitrary amount of ancillary qubits available, the circuit size for preparing n-qubit d-sparse quantum states is Θ(logdndn + n). © 2024, CC BY.

关键词： Qubits

Lightcone Bounds for quantum Circuit Mapping via Uncomplexity

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arXiv 2024年

作者： Steinberg, Matthew Bandić, Medina Szkudlarek, Sacha Almudever, Carmen G. Sarkar, Aritra Feld, Sebastian Quantum Computing Division QuTech Delft University of Technology Delft Netherlands Department of Quantum & Computer Engineering Delft University of Technology Delft Netherlands Computer Engineering Department Technical University of Valencia Valencia Spain

Efficiently mapping quantum circuits onto hardware is an integral part of the quantum compilation process, wherein a circuit is modified in accordance with the stringent architectural demands of a quantum processor. Many techniques exist for solving the quantum circuit mapping problem, in addition to several theoretical perspectives that relate quantum circuit mapping to problems in classical computer science. This work considers a novel perspective on quantum circuit mapping, in which the routing process of a simplified circuit is viewed as a composition of quantum operations acting on density matrices representing the quantum circuit and processor. Drawing on insight from recent advances in quantum circuit complexity and information geometry, we show that a minimal SWAP-gate count for executing a quantum circuit on a device emerges via the minimization of the distance between quantum states using the quantum Jensen-Shannon divergence, which we dub the lightcone bound. Additionally, we develop a novel initial placement algorithm based on a graph similarity search that selects the partition nearest to a graph isomorphism between interaction and coupling graphs. From these two ingredients, we construct an algorithm for calculating the lightcone bound, which is directly compared alongside the IBM Qiskit compiler for over 600 realistic benchmark experiments, as well as against a brute-force method for smaller benchmarks. In our simulations, we unambiguously find that neither the brute-force method nor the Qiskit compiler surpasses our bound, signaling utility for estimating minimal overhead when realizing quantum algorithms on constrained quantum hardware. This work also constitutes the first use of quantum circuit uncomplexity to practically-relevant quantum computing. We anticipate that this method may have diverse applicability outside of the scope of quantum information science. Copyright © 2024, The Authors. All rights reserved.

关键词： quantum computers

Deep Learning for Channel Prediction in Non-Stationary Wireless Fading Environments

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Deep Learning for Channel Prediction in Non-Stationary Wirel...

2024 IEEE International Conference on Intelligent Signal Processing and Effective Communication Technologies, INSPECT 2024

作者： Upadhyay, Deepak Sharma, Kunj Bihari Gupta, Mridul Upadhyay, Abhay Venu, Nookala Graphic Era Hill University Dept. of Computer Science and Engineering Dehradun India Graphic Era deemed to be University Dept. of Computer Science and Engineering Dehradun India Graphic Era deemed to be University Dept. of Electronics and Communication Engineering Dehradun India Data Science and Quantum Computing ABV Indian Institute of Information Technology and Management Gwalior India

ISBN: (纸本)9798350379525

In non-stationary wireless fading channels deep learning models are effective in predicting channel states as indicated by this study. This work compared the LSTM and GRU models with autoregressive methods or Kalman filter, implying that deep learning is indeed able to capture temporal dependence between variables and was likely more adapted than linear method when dealing with many changes in dynamics. From the perspective of pre-processing data, keys like attention mechanism and transfer learning were decisive elements in helping them to improve prediction scores and make models more robust. These results showed that these enhanced procedures allow the models to generalise over a wide range of non-stationary situations, generating consistent performance in various diverse environments. This study indicates the promise of deep learning for enhancing wireless network operation, which could lead to greater self-awareness and utilization features in emerging future-generation wireless systems. © 2024 IEEE.

关键词： Prediction models