QUROPE Quantum Information Processing and Communication in Europe

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

Author(s): Philip Ball

The formation of a black hole from light alone is permitted by general relativity, but a new study says quantum physics rules it out.

[Physics 17, 119] Published Fri Jul 26, 2024

Author(s): Da-Jian Zhang and D. M. Tong

Learning physical properties of high-dimensional states is crucial for developing quantum technologies but usually consumes an exceedingly large number of samples which are difficult to afford in practice. In this Letter, we use the methodology of quantum metrology to tackle this difficulty, proposi…

[Phys. Rev. Lett. 133, 040202] Published Thu Jul 25, 2024

Author(s): Marric Stephens

Researchers show that atoms that escape from an atom array can be replaced on the fly—an important step toward operating a large-scale neutral-atom quantum computer.

[Physics 17, s93] Published Thu Jul 25, 2024

Author(s): Francesco Anna Mele, Farzin Salek, Vittorio Giovannetti, and Ludovico Lami

Quantum optical systems are typically affected by two types of noise: photon loss and dephasing. Despite extensive research on each noise process individually, a comprehensive understanding of their combined effect is still lacking. A crucial problem lies in determining the values of loss and dephas…

[Phys. Rev. A 110, 012460] Published Thu Jul 25, 2024

Author(s): Alan Kahan and Cecilia Cormick

Dissipative quantum systems can under appropriate conditions exhibit bi- or multipartite entanglement at the steady state. The presence and properties of these quantum correlations depend on the relevant model parameters. Here, we characterize the steady-state entanglement in connection with the spa…

[Phys. Rev. A 110, 012461] Published Thu Jul 25, 2024

Author(s): Zijian Zhang, Lingxuan Feng, and Shunlong Luo

From both intuitive and physical perspectives, it is generally recognized that within a resource theory framework, free operations cannot broadcast a resource state due to their inability to generate resource from free states. In the stabilizer formalism of fault-tolerant quantum computation, the ba…

[Phys. Rev. A 110, 012462] Published Thu Jul 25, 2024

Author(s): Tatsuhiko Shirai and Takashi Mori

Markovian open many-body quantum systems display complicated relaxation dynamics. The spectral gap of the Liouvillian characterizes the asymptotic decay rate towards the stationary state, but it has recently been pointed out that the spectral gap does not necessarily determine the overall relaxation…

[Phys. Rev. Lett. 133, 040201] Published Wed Jul 24, 2024

Author(s): Charles Day

How an alga synchronizes its two flapping cilia to propel itself is revealed in a tabletop experiment with chains of mobile robots.

[Physics 17, s81] Published Wed Jul 24, 2024

Author(s): Melika Babakan, Arman Kashef, and Laleh Memarzadeh

We study entanglement degradation when one share of an entangled pair experiences noise. We consider the dissipative Landau-Zener model for describing local noise. The dissipative Landau-Zener model provides a convenient setting for modeling entanglement degradation with applications in quantum netw…

[Phys. Rev. A 110, 012456] Published Wed Jul 24, 2024

Author(s): Deepesh Singh, Austin P. Lund, and Peter P. Rohde

Cluster states are the essential resource used in the implementation of fusion-based quantum computation (FBQC). We introduce a method to generate high-fidelity optical cluster states by utilizing the concept of unitary averaging. This error-averaging technique is entirely passive and can be readily…

[Phys. Rev. A 110, 012457] Published Wed Jul 24, 2024

Author(s): Hongshun Yao, Xia Liu, Chengkai Zhu, and Xin Wang

Quantum broadcasting is central to quantum information processing and characterizes the correlations within quantum states. Nonetheless, traditional quantum broadcasting encounters inherent limitations dictated by the principles of quantum mechanics. In a previous study, Parzygnat et al. [Phys. Rev.…

[Phys. Rev. A 110, 012458] Published Wed Jul 24, 2024

Author(s): Zhu-yao Jin and Jun Jing

A stable and high-quality single-magnon state is desired by the single-magnon source for quantum-information application with a macroscopic spin system. We consider a hybrid system where a magnon mode is directly coupled to a nonresonant superconducting qubit via the exchange interaction. The magnon…

[Phys. Rev. A 110, 012459] Published Wed Jul 24, 2024

Author(s): David Ehrenstein

An ordered pattern of atomic spins with possible uses in computing can become more ordered if shaken at the right frequency.

[Physics 17, s90] Published Tue Jul 23, 2024

Author(s): Luke Coffman, Akshay Seshadri, Graeme Smith, and Jacob L. Beckey

Despite multipartite entanglement being a global property of a quantum state, a number of recent works have made it clear that it can be quantified using only local measurements. This is appealing because local measurements are the easiest to implement on current quantum hardware. However, it remain…

[Phys. Rev. A 110, 012454] Published Tue Jul 23, 2024

Author(s): Christopher F. Kane, Niladri Gomes, and Michael Kreshchuk

We present several improvements to the recently developed ground-state preparation algorithm based on the quantum eigenvalue transformation for unitary matrices (QETU), apply this algorithm to a lattice formulation of U(1) gauge theory in (2+1) dimensions, as well as propose an alternative applicati…

[Phys. Rev. A 110, 012455] Published Tue Jul 23, 2024

Author(s): U. Alushi, W. Górecki, S. Felicetti, and R. Di Candia

We compare critical quantum sensing to passive quantum strategies to perform frequency estimation, in the case of single-mode quadratic Hamiltonians. We show that, while in the unitary case both strategies achieve precision scaling quadratic with the number of photons, in the presence of dissipation…

[Phys. Rev. Lett. 133, 040801] Published Mon Jul 22, 2024

Author(s): Sarah Marzen

Both the predictive power and the memory storage capability of an artificial neural network called a reservoir computer increase when time delays are added into how the network processes signals, according to a new model.

[Physics 17, 111] Published Mon Jul 22, 2024