QUROPE Quantum Information Processing and Communication in Europe

Author(s): Iris Ulčakar and Zala Lenarčič

Integrable systems offer rare examples of solvable many-body problems in the quantum world. Because of the fine-tuned structure, their realization in nature and experiment is never completely accurate, and therefore effects of integrability are observed only transiently. One way to overcome this lim…

[Phys. Rev. Lett. 132, 230402] Published Tue Jun 04, 2024

Author(s): Guilherme Zambon and Diogo O. Soares-Pinto

In the dynamics of open quantum systems, information may propagate in time through either the system or the environment, giving rise to Markovian and non-Markovian temporal correlations, respectively. However, despite their notable coexistence in most physical situations, it is not yet clear how the…

[Phys. Rev. A 109, 062401] Published Mon Jun 03, 2024

Author(s): G.-X. Wang, Y.-K. Wu, R. Yao, W.-Q. Lian, Z.-J. Cheng, Y.-L. Xu, C. Zhang, Y. Jiang, Y.-Z. Xu, B.-X. Qi, P.-Y. Hou, Z.-C. Zhou, L. He, and L.-M. Duan

The spin-boson model is a prototypical model for open quantum dynamics. Here we simulate the spin-boson model using a chain of trapped ions in which a spin is coupled to a structured reservoir of bosonic modes. We engineer the spectral density of the reservoir by adjusting the ion number, the target…

[Phys. Rev. A 109, 062402] Published Mon Jun 03, 2024

Author(s): Minjin Choi, Jeonghyeon Shin, Gunho Lee, and Eunok Bae

Quantum teleportation is an essential application of quantum entanglement. The examination of teleportation fidelity in two-party standard teleportation schemes reveals a critical threshold distinguishing separable and entangled states. For separable states, their teleportation fidelities cannot exc…

[Phys. Rev. A 109, 062403] Published Mon Jun 03, 2024

Author(s): Ruidi Zhu, Ciara Pike-Burke, and Florian Mintert

The experimental evaluation of many quantum mechanical quantities requires the estimation of several directly measurable observables, such as local observables. Due to the necessity to repeat experiments on individual quantum systems in order to estimate expectation values of observables, the questi…

[Phys. Rev. A 109, 062404] Published Mon Jun 03, 2024

Author(s): Agung Budiyono

Kirkwood-Dirac (KD) quasiprobability is a quantum analog of classical phase space probability. It offers an informationally complete representation of quantum state wherein the quantumness associated with quantum noncommutativity manifests in its nonclassical values, i.e., the nonreal and/or negativ…

[Phys. Rev. A 109, 062405] Published Mon Jun 03, 2024

Author(s): Yu Wang and Wei Cui

Classical shadow tomography, harnessing randomized informationally complete (IC) measurements, provides an effective avenue for predicting many properties of unknown quantum states. In n-qubit systems, projections onto 2n+1 mutually unbiased bases (MUBs) are widely recognized as minimal and optimal …

[Phys. Rev. A 109, 062406] Published Mon Jun 03, 2024

Author(s): Tenghui Wang, Feng Wu, Fei Wang, Xizheng Ma, Gengyan Zhang, Jianjun Chen, Hao Deng, Ran Gao, Ruizi Hu, Lu Ma, Zhijun Song, Tian Xia, Make Ying, Huijuan Zhan, Hui-Hai Zhao, and Chunqing Deng

Fast and high-fidelity qubit initialization is crucial for low-frequency qubits such as fluxonium, and in applications of many quantum algorithms and quantum error correction codes. In a circuit quantum electrodynamics system, the initialization is typically achieved by transferring the state betwee…

[Phys. Rev. Lett. 132, 230601] Published Mon Jun 03, 2024

Author(s): Robin Krebs and Mariami Gachechiladze

A deep understanding of quantum entanglement is vital for advancing quantum technologies. The strength of entanglement can be quantified by counting the degrees of freedom that are entangled, which results in a quantity called the Schmidt number. A particular challenge is to identify the strength of…

[Phys. Rev. Lett. 132, 220203] Published Fri May 31, 2024

Author(s): Vladislav Popkov, Xin Zhang, Frank Göhmann, and Andreas Klümper

We propose a qubit basis composed of transverse spin helices with kinks. Unlike the usual computational basis, this chiral basis is well-suited for describing quantum states with nontrivial topology. Choosing appropriate parameters the operators of the transverse spin components, σnx and σny, become…

[Phys. Rev. Lett. 132, 220404] Published Fri May 31, 2024

Author(s): Patrycja Łydżba, Peter Prelovšek, and Marcin Mierzejewski

Hilbert space fragmentation is an ergodicity-breaking phenomenon, in which the Hamiltonian shatters into exponentially many dynamically disconnected sectors. In many fragmented systems, these sectors can be labeled by statistically localized integrals of motion, which are nonlocal operators. We stud…

[Phys. Rev. Lett. 132, 220405] Published Fri May 31, 2024

Author(s): Irma Avdic and David A. Mazziotti

Classical shadow tomography provides a randomized scheme for approximating the quantum state and its properties at reduced computational cost with applications in quantum computing. In this Letter we present an algorithm for realizing fewer measurements in the shadow tomography of many-body systems.…

[Phys. Rev. Lett. 132, 220802] Published Fri May 31, 2024

Author(s): Xian Shi

In this work, we present a coherence measure based on the quantum optimal transport cost in terms of the convex roof extended method. We also obtain the analytical solutions of the quantifier for pure states. We also propose an operational interpretation of the coherence measure for pure states.

[Phys. Rev. A 109, 052443] Published Fri May 31, 2024

Author(s): Shin-Liang Chen and Jens Eisert

We develop a framework for characterizing quantum temporal correlations in a general temporal scenario, in which an initial quantum state is measured, sent through a quantum channel, and finally measured again. This framework does not make any assumptions on the system nor on the measurements, namel…

[Phys. Rev. Lett. 132, 220201] Published Thu May 30, 2024

Author(s): Nicolò Piccione, Léa Bresque, Andrew N. Jordan, Robert S. Whitney, and Alexia Auffèves

An effective time-dependent Hamiltonian can be implemented by making a quantum system fly through an inhomogeneous potential, realizing, for example, a quantum gate on its internal degrees of freedom. However, flying systems have a spatial spread that will generically entangle the internal and spati…

[Phys. Rev. Lett. 132, 220403] Published Thu May 30, 2024

Author(s): Christian Ufrecht, Laura S. Herzog, Daniel D. Scherer, Maniraman Periyasamy, Sebastian Rietsch, Axel Plinge, and Christopher Mutschler

Circuit cutting, the partitioning of quantum circuits into smaller independent fragments, has become a promising avenue for scaling up current quantum-computing experiments. Here, we introduce a scheme for joint cutting of two-qubit rotation gates based on a virtual gate-teleportation protocol. With…

[Phys. Rev. A 109, 052440] Published Thu May 30, 2024

Author(s): Yagnik Chatterjee, Eric Bourreau, and Marko J. Rančić

NP-hard problems are not believed to be exactly solvable through general polynomial time algorithms. Hybrid quantum-classical algorithms to address such combinatorial problems have been of great interest in the past few years. Such algorithms are heuristic in nature and aim to obtain an approximate …

[Phys. Rev. A 109, 052441] Published Thu May 30, 2024

Author(s): Bin Liu, Zhonghao Liang, Wei Huang, Fei Gao, Jiayi Yuan, and Bingjie Xu

Quantum private query (QPQ) faces many challenges in practical applications. At present, some scholars have made substantial work on overcoming channel loss, channel noise, and nonideal light sources, respectively. However, a protocol that would overcome all three of these problems has yet to materi…

[Phys. Rev. A 109, 052442] Published Thu May 30, 2024

Author(s): Yingjia Lin, Shilin Huang, and Kenneth R. Brown

For quantum error correction codes the required number of measurement rounds typically increases with the code distance when measurements are faulty. Single-shot error correction allows for an error threshold with only one round of noisy syndrome measurements regardless of the code size. Here we imp…

[Phys. Rev. A 109, 052438] Published Wed May 29, 2024

Author(s): Yuntao Tsui and Sunho Kim

The wave-particle duality, one of the expressions of Bohr complementarity, is usually quantified by path predictability and the visibility of interference fringes. With the development of quantum resource theory, quantitative analysis of wave-particle duality is increasing, most of which are express…

[Phys. Rev. A 109, 052439] Published Wed May 29, 2024