QUROPE Quantum Information Processing and Communication in Europe

Author(s): Y. S. Teo, S. U. Shringarpure, H. Jeong, N. Prasannan, B. Brecht, C. Silberhorn, M. Evans, D. Mogilevtsev, and L. L. Sánchez-Soto

Identifying a reasonably small Hilbert space that completely describes an unknown quantum state is crucial for efficient quantum information processing. We introduce a general dimension-certification protocol for both discrete and continuous variables that is fully evidence based, relying solely on …

[Phys. Rev. Lett. 133, 050204] Published Wed Jul 31, 2024

Author(s): Tobias Haug and M. S. Kim

Generalization is the ability of machine learning models to make accurate predictions on new data by learning from training data. However, understanding generalization of quantum machine learning models has been a major challenge. Here, we introduce the data quantum Fisher information metric (DQFIM)…

[Phys. Rev. Lett. 133, 050603] Published Wed Jul 31, 2024

Author(s): Ryan Wilkinson

A way to determine the flavors of ultrahigh-energy cosmic neutrinos observed by future detectors could help scientists understand the origin of these elusive particles.

[Physics 17, s87] Published Wed Jul 31, 2024

Author(s): Zhangjie Qin, Daniel Azses, Eran Sela, Robert Raussendorf, and V. W. Scarola

Computational power in measurement-based quantum computing stems from the symmetry-protected topological (SPT) order of entangled resource states. However, resource states are prone to preparation errors. We introduce a quantum error correction approach using redundant nonlocal symmetry of the resou…

[Phys. Rev. A 110, 012465] Published Wed Jul 31, 2024

Author(s): M. Suman, S. Aravinda, and Ranjan Modak

The quantum speed limit (QSL) is the lower bound on the time required for a state to evolve to a desired final state under a given Hamiltonian evolution. Three well-known QSLs exist: the Mandelstam-Tamm (MT), Margolus-Levitin (ML), and dual ML (ML*) bounds. We consider one-dimensional systems that u…

[Phys. Rev. A 110, 012466] Published Wed Jul 31, 2024

Author(s): Julio I. de Vicente

An answer to a decades-old question in the theory of quantum entanglement raises more questions about this quirky phenomenon.

[Phys. Rev. Lett. 133, 050202] Published Tue Jul 30, 2024

Author(s): Wei Wu and Jun-Hong An

The nonequilibrium fluctuation relation is a cornerstone of quantum thermodynamics. It is widely believed that the system-bath heat exchange obeys the famous Jarzynski-Wójcik fluctuation theorem. However, this theorem is established in the Born-Markovian approximation under the weak-coupling conditi…

[Phys. Rev. Lett. 133, 050401] Published Tue Jul 30, 2024

Author(s): Alireza Seif, Yu-Xin Wang (王语馨), Ramis Movassagh, and Aashish A. Clerk

We study the interplay between measurement-induced dynamics and conditional unitary evolution in quantum systems. We numerically and analytically investigate commuting random measurement and feed forward (MFF) processes and find a sharp transition in their ability to generate entanglement negativity…

[Phys. Rev. Lett. 133, 050402] Published Tue Jul 30, 2024

Author(s): Yuki Takeuchi

There are two types of universality in measurement-based quantum computation (MBQC): strict and computational. It is well known that the former is stronger than the latter. We present a method of transforming from a certain type of computationally universal MBQC to a strictly universal one. Our meth…

[Phys. Rev. Lett. 133, 050601] Published Tue Jul 30, 2024

Author(s): V. G. Matsos, C. H. Valahu, T. Navickas, A. D. Rao, M. J. Millican, X. C. Kolesnikow, M. J. Biercuk, and T. R. Tan

Encoding logical qubits in bosonic modes provides a potentially hardware-efficient implementation of fault-tolerant quantum information processing. Here, we demonstrate high-fidelity and deterministic preparation of highly nonclassical bosonic states in the mechanical motion of a trapped ion. Our ap…

[Phys. Rev. Lett. 133, 050602] Published Tue Jul 30, 2024

Author(s): Michael Schirber

Nelly Ng studies “quantum catalysts”—extra qubits or other elements that can help perform a quantum information process, in the same way that an extra tower helps solve a classic logic game.

[Physics 17, 109] Published Tue Jul 30, 2024

Author(s): Charles Day

Experiments at the Joint European Torus make the case for using gamma rays to determine the fusion reaction rate in a magnetically confined plasma.

[Physics 17, s59] Published Tue Jul 30, 2024

Author(s): Ryan Wilkinson

An answer to a decades-old question in the theory of quantum entanglement raises more questions about this quirky phenomenon.

[Physics 17, s83] Published Tue Jul 30, 2024

Author(s): Yi-Hao Kang, Yu Wang, Qi-Ping Su, Guo-Qiang Zhang, Wei Feng, and Chui-Ping Yang

We propose a scheme for realizing parity measurement of cat-state qubits based on a topological quantum phase transition. The cat-state qubits, formed by the bosonic modes in the Kerr-nonlinear resonators with two-photon squeezing drives, couple with a superconducting qubit in the center. We demonst…

[Phys. Rev. A 110, 012463] Published Tue Jul 30, 2024

Author(s): Anna Beever, Maria Violaris, Chiara Marletto, and Vlatko Vedral

Here we investigate the role of quantum interference in the quantum homogenizer, whose convergence properties model a thermalization process. In the original quantum homogenizer protocol, a system qubit converges to the state of identical reservoir qubits through partial-swap interactions, that allo…

[Phys. Rev. A 110, 012464] Published Tue Jul 30, 2024

Author(s): Lin Htoo Zaw

In circuit and cavity quantum electrodynamics devices where control qubits are dispersively coupled to high-quality-factor cavities, characteristic functions of cavity states can be directly probed with conditional displacement (CD) gates. In this Letter, I propose a method to certify non-Gaussian e…

[Phys. Rev. Lett. 133, 050201] Published Mon Jul 29, 2024

Author(s): Han-Ning Dai and Yu-Ao Chen

By reducing the effect of systematic errors, researchers have created an atomic clock that sets a new record for precision.

[Physics 17, 118] Published Mon Jul 29, 2024

Author(s): Chengjie Zhang, Sophia Denker, Ali Asadian, and Otfried Gühne

Characterizing entanglement is central for quantum information science. Special observables which indicate entanglement, so-called entanglement witnesses, are a widely used tool for this task. The construction of these witnesses typically relies on the observation that quantum states with a high fid…

[Phys. Rev. Lett. 133, 040203] Published Fri Jul 26, 2024

Author(s): Cheng Xi, Xiangjing Liu, Hongfeng Liu, Keyi Huang, Xinyue Long, Daniel Ebler, Xinfang Nie, Oscar Dahlsten, and Dawei Lu

We experimentally probe the interplay of the quantum switch with the laws of thermodynamics. The quantum switch places two channels in a superposition of orders and may be applied to thermalizing channels. Quantum-switching thermal channels has been shown to give apparent violations of the second la…

[Phys. Rev. Lett. 133, 040401] Published Fri Jul 26, 2024

Author(s): Luis Pedro García-Pintos, Kishor Bharti, Jacob Bringewatt, Hossein Dehghani, Adam Ehrenberg, Nicole Yunger Halpern, and Alexey V. Gorshkov

We upper bound and lower bound the optimal precision with which one can estimate an unknown Hamiltonian parameter via measurements of Gibbs thermal states with a known temperature. The bounds depend on the uncertainty in the Hamiltonian term that contains the parameter and on the term’s degree of no…

[Phys. Rev. Lett. 133, 040802] Published Fri Jul 26, 2024