QUROPE Quantum Information Processing and Communication in Europe

Author(s): Daniel Honciuc Menendez, Annie Ray, and Michael Vasmer

Quantum computers promise to solve problems that are intractable for classical computers, but qubits are vulnerable to many sources of error, limiting the depth of the circuits that can be reliably executed on today's quantum hardware. Quantum error correction has been proposed as a solution to this…

[Phys. Rev. A 109, 062438] Published Fri Jun 28, 2024

Author(s): B. Sharmila, F. M. Souza, H. M. Vasconcelos, and L. Sanz

We investigate the generation of an entangled electron pair emerging from a system composed of two quantum dots attached to a superconductor Cooper-pair beam splitter. We take into account three processes: crossed Andreev reflection, cotunneling, and Coulomb interaction. Together, these processes pl…

[Phys. Rev. A 109, 062439] Published Fri Jun 28, 2024

Author(s): Patryk Lipka-Bartosik, Henrik Wilming, and Nelly H. Y. Ng

A branch of quantum information is concerned with transformations that are possible given certain resources: for example, quantum teleportation moves a quantum state from one place to another, aided by entanglement and classical communication. Certain other tasks are provably impossible. But, as surveyed in this review, a surprising fact is that some tasks become possible if another quantum state is present, even if this state is returned untouched at the end of the task. This “quantum catalysis” enables a large variety of interesting tasks, with applications ranging from cryptography to thermodynamics.

[Rev. Mod. Phys. 96, 025005] Published Thu Jun 27, 2024

Author(s): Xingrui Song, Flavio Salvati, Chandrashekhar Gaikwad, Nicole Yunger Halpern, David R. M. Arvidsson-Shukur, and Kater Murch

Quantum sensing can benefit from entanglement protocols that can be interpreted as allowing qubits to go backward in time to choose an optimal initial state.

[Phys. Rev. Lett. 132, 260801] Published Thu Jun 27, 2024

Author(s): Nikhil Karthik

Researchers at CERN have significantly increased the precision of the measured value of the top-quark mass, a key input for making standard-model calculations.

[Physics 17, s57] Published Thu Jun 27, 2024

Author(s): Michael Schirber

Quantum sensing can benefit from entanglement protocols that can be interpreted as allowing qubits to go backward in time to choose an optimal initial state.

[Physics 17, s76] Published Thu Jun 27, 2024

Author(s): Ryan J. Marshman, Deepesh Singh, Timothy C. Ralph, and Austin P. Lund

We consider the impact of the unitary-averaging framework on single- and two-mode linear optical gates. We demonstrate that this allows a trade-off between the probability of success and gate fidelity, with perfect fidelity gates being achievable for a finite decrease in the probability of success, …

[Phys. Rev. A 109, 062436] Published Thu Jun 27, 2024

Author(s): Baptiste Anselme Martin, Thomas Ayral, François Jamet, Marko J. Rančić, and Pascal Simon

Matrix product states (MPSs) and matrix product operators (MPOs) have been proven to be a powerful tool to study quantum many-body systems but are restricted to moderately entangled states as the number of parameters scales exponentially with the entanglement entropy. While MPSs can efficiently find…

[Phys. Rev. A 109, 062437] Published Thu Jun 27, 2024

Author(s): Gabriel M. Lando, Olivier Giraud, and Denis Ullmo

We study the time evolution of mean values of quantum operators in a regime plagued by two difficulties: the smallness of ℏ and the presence of strong and ubiquitous classical chaos. While numerics become too computationally expensive for purely quantum calculations as ℏ→0, methods that take advanta…

[Phys. Rev. Lett. 132, 260401] Published Wed Jun 26, 2024

Author(s): Michael Schirber

A vibrating nanobeam could be used to share information between distant solid-state spin qubits, potentially allowing use of these qubits in complex computations.

[Physics 17, s71] Published Wed Jun 26, 2024

Author(s): Rachel Berkowitz

Bright light triggers the chloroplast of a bioluminescent algae to fold into a pattern that minimizes the chloroplast’s exposed area.

[Physics 17, 103] Published Tue Jun 25, 2024

Author(s): Charles Day

A long-running experiment aboard the International Space Station has found an unexpected population of cosmic rays made of heavy hydrogen ions.

[Physics 17, s74] Published Tue Jun 25, 2024

Author(s): Yi Tao, Ting Chen, Hongyang Wang, Jie Zhang, Ting Zhang, Yi Xie, Pingxing Chen, and Wei Wu

In a trapped-ion system, accurate thermometry of ions is crucial for precisely evaluating the system state and performing quantum operations. However, when the motional state of a single ion is far away from the ground state, the spatial dimensionality of the phonon state sharply increases. Then it …

[Phys. Rev. A 109, 062434] Published Tue Jun 25, 2024

Author(s): Raphaël Mothe, Cyril Branciard, and Alastair A. Abbott

The quantum switch, the canonical example of a process with indefinite causal order, has been claimed to provide various advantages over processes with definite causal orders for some particular tasks in the field of quantum metrology. In this work, we argue that some of these advantages in fact do …

[Phys. Rev. A 109, 062435] Published Tue Jun 25, 2024

Author(s): M. Cristina Volpe

Neutrinos can change flavors due to their nonzero masses and mixings as well as their interactions with matter and other neutrinos. In dense astrophysical environments, such as core-collapse supernovae or neutron star mergers, the problem of neutrino flavor evolution becomes very complex. Connections to other domains such as quantum information theory have been uncovered. Understanding the neutrino flavor evolution in dense environments can shed light on the dynamics of massive star explosions and the origin of heavy elements in the Universe and is important for future observations of supernova neutrinos.

[Rev. Mod. Phys. 96, 025004] Published Mon Jun 24, 2024

Author(s): Elisabeth Kreuzgruber, Richard Wagner, Niels Geerits, Hartmut Lemmel, and Stephan Sponar

Leggett-Garg inequalities (LGIs) have been proposed in order to assess how far the predictions of quantum mechanics defy “macroscopic realism.” With LGIs, correlations of measurements performed on a single system at different times are described. We report on an experiment that demonstrates the viol…

[Phys. Rev. Lett. 132, 260201] Published Mon Jun 24, 2024

Author(s): Gary Zabow

A new technique combining magnetic resonance imaging and x-ray fluorescence can characterize, with single-neuron resolution, the presence of toxic forms of iron that might be associated with neurodegenerative diseases.

[Physics 17, 101] Published Mon Jun 24, 2024

Author(s): Chien-Hung Cho, Dominic W. Berry, and Min-Hsiu Hsieh

Hamiltonian simulation is a major application of quantum computing, for example, enabling prediction of the properties of molecules. Prior work has used product formulas with randomization to improve performance, but has only yielded modest improvements over the excellent performance provided by det…

[Phys. Rev. A 109, 062431] Published Mon Jun 24, 2024

Author(s): Ole Sönnerborn

Nonadiabatic holonomic quantum computation has been proposed as a method to implement quantum logic gates with robustness comparable to that of adiabatic holonomic gates but with shorter execution times. In this paper, we establish an isoholonomic inequality for quantum gates, which provides a lower…

[Phys. Rev. A 109, 062433] Published Mon Jun 24, 2024

Author(s): Suirong He, Penghui Ouyang, Haiyan Gao, Yufen Li, Jiaxing He, and L. F. Wei

Microwave single-photon detection is one of the critical tasks for the implementation of the desired microwave quantum information processing. Given the detection efficiency of the demonstrated microwave single-photon detector is still very limited, here, we propose a nonreciprocity detector array t…

[Phys. Rev. A 109, 062430] Published Mon Jun 24, 2024