Quantum

Paper

Measurement disturbance and conservation laws in quantum mechanics

M. Hamed Mohammady, Takayuki Miyadera, and Leon Loveridge,

Quantum 7, 1033 (2023).

Measurement error and disturbance, in the presence of conservation laws, are analysed in general operational terms. We provide novel quantitative bounds demonstrating necessary conditions un…

Paper

The $2T$-qutrit, a two-mode bosonic qutrit

Aurélie Denys and Anthony Leverrier,

Quantum 7, 1032 (2023).

Quantum computers often manipulate physical qubits encoded on two-level quantum systems. Bosonic qubit codes depart from this idea by encoding information in a well-chosen subspace of an inf…

Paper

On efficient quantum block encoding of pseudo-differential operators

Haoya Li, Hongkang Ni, and Lexing Ying,

Quantum 7, 1031 (2023).

Block encoding lies at the core of many existing quantum algorithms. Meanwhile, efficient and explicit block encodings of dense operators are commonly acknowledged as a challenging problem.…

Paper

On Quantum Speedups for Nonconvex Optimization via Quantum Tunneling Walks

Yizhou Liu, Weijie J. Su, and Tongyang Li,

Quantum 7, 1030 (2023).

Classical algorithms are often not effective for solving nonconvex optimization problems where local minima are separated by high barriers. In this paper, we explore possible quantum speedup…

Paper

Geometric phases along quantum trajectories

Ludmila Viotti, Ana Laura Gramajo, Paula I. Villar, Fernando C. Lombardo, and Rosario Fazio,

Quantum 7, 1029 (2023).

A monitored quantum system undergoing a cyclic evolution of the parameters governing its Hamiltonian accumulates a geometric phase that depends on the quantum trajectory followed by the syst…

Paper

Causal structure in the presence of sectorial constraints, with application to the quantum switch

Nick Ormrod, Augustin Vanrietvelde, and Jonathan Barrett,

Quantum 7, 1028 (2023).

Existing work on quantum causal structure assumes that one can perform arbitrary operations on the systems of interest. But this condition is often not met. Here, we extend the framework for…

Paper

Relaxation of Multitime Statistics in Quantum Systems

Neil Dowling, Pedro Figueroa-Romero, Felix A. Pollock, Philipp Strasberg, and Kavan Modi,

Quantum 7, 1027 (2023).

Equilibrium statistical mechanics provides powerful tools to understand physics at the macroscale. Yet, the question remains how this can be justified based on a microscopic quantum descript…

Paper

Scalable and Flexible Classical Shadow Tomography with Tensor Networks

Ahmed A. Akhtar, Hong-Ye Hu, and Yi-Zhuang You,

Quantum 7, 1026 (2023).

Classical shadow tomography is a powerful randomized measurement protocol for predicting many properties of a quantum state with few measurements. Two classical shadow protocols have been ex…

Paper

Linear optics and photodetection achieve near-optimal unambiguous coherent state discrimination

Jasminder S. Sidhu, Michael S. Bullock, Saikat Guha, and Cosmo Lupo,

Quantum 7, 1025 (2023).

Coherent states of the quantum electromagnetic field, the quantum description of ideal laser light, are prime candidates as information carriers for optical communications. A large body of l…

Paper

Quantum Rabi interferometry of motion and radiation

Kimin Park, Petr Marek, Ulrik L. Andersen, and Radim Filip,

Quantum 7, 1024 (2023).

The precise determination of a displacement of a mechanical oscillator or a microwave field in a predetermined direction in phase space can be carried out with trapped ions or superconductin…

Paper

Entanglement entropy production in Quantum Neural Networks

Marco Ballarin, Stefano Mangini, Simone Montangero, Chiara Macchiavello, and Riccardo Mengoni,

Quantum 7, 1023 (2023).

Quantum Neural Networks (QNN) are considered a candidate for achieving quantum advantage in the Noisy Intermediate Scale Quantum computer (NISQ) era. Several QNN architectures have been prop…

Paper

Universal equilibration dynamics of the Sachdev-Ye-Kitaev model

Soumik Bandyopadhyay, Philipp Uhrich, Alessio Paviglianiti, and Philipp Hauke,

Quantum 7, 1022 (2023).

Equilibrium quantum many-body systems in the vicinity of phase transitions generically manifest universality. In contrast, limited knowledge has been gained on possible universal characteris…

Paper

Continuous majorization in quantum phase space

Zacharie Van Herstraeten, Michael G. Jabbour, and Nicolas J. Cerf,

Quantum 7, 1021 (2023).

We explore the role of majorization theory in quantum phase space. To this purpose, we restrict ourselves to quantum states with positive Wigner functions and show that the continuous versio…

Paper

Circuits of space and time quantum channels

Pavel Kos and Georgios Styliaris,

Quantum 7, 1020 (2023).

Exact solutions in interacting many-body systems are scarce but extremely valuable since they provide insights into the dynamics. Dual-unitary models are examples in one spatial dimension wh…

Paper

Quantum key distribution rates from semidefinite programming

Mateus Araújo, Marcus Huber, Miguel Navascués, Matej Pivoluska, and Armin Tavakoli,

Quantum 7, 1019 (2023).

Computing the key rate in quantum key distribution (QKD) protocols is a long standing challenge. Analytical methods are limited to a handful of protocols with highly symmetric measurement ba…

Paper

Exact and efficient Lanczos method on a quantum computer

William Kirby, Mario Motta, and Antonio Mezzacapo,

Quantum 7, 1018 (2023).

We present an algorithm that uses block encoding on a quantum computer to exactly construct a Krylov space, which can be used as the basis for the Lanczos method to estimate extremal eigenva…

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