Physical Review A最新文献

{"title":"Parallel two-qubit entangling gates via a quantum nondemolition interaction controlled by rotation","authors":"E. A. Vashukevich, T. Yu. Golubeva","doi":"10.1103/physreva.110.032616","DOIUrl":"https://doi.org/10.1103/physreva.110.032616","url":null,"abstract":"The paper presents an analysis of entangling and nonlocal operations in a quantum nondemolition (QND) interaction between multimode light with orbital angular momentum and an atomic ensemble. A protocol consists of two QND operations with rotations of quadratures of atomic spin coherence and light between them. This protocol provides a wide range of two-qubit operations, while the multimode nature of the chosen degrees of freedom allows the implementation of parallel operations over multiple two-qubit systems. We have used the formalism of equivalence classes and local invariants to evaluate the properties of two-qubit transformations. It is shown that, when selecting suitable values of the governing parameters, such as the duration of each of the two QND interactions and the rotation angles of the qubits, the protocol allows to realize a deterministic nonlocal SWAP operation and entangling <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msqrt><mtext>SWAP</mtext></msqrt></math> operation with probability <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mfrac><mn>1</mn><mn>3</mn></mfrac></math>.","PeriodicalId":20146,"journal":{"name":"Physical Review A","volume":"27 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142262772","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Separation of various higher-order effects in the ionization of helium by proton impact","authors":"S. Majumdar, S. Bastola, A. Hasan, R. Lomsadze, M. Schulz","doi":"10.1103/physreva.110.032814","DOIUrl":"https://doi.org/10.1103/physreva.110.032814","url":null,"abstract":"We have measured fully differential cross sections (FDCSs) for ionization of helium by 75 keV proton impact. Data were analyzed for electrons ejected into the scattering plane at projectile energy losses well below and above the matching velocity and for scattering angles ranging between 0.1 and 0.5 mrad. Earlier, we observed clear signatures of the postcollision interaction (PCI) at the matching velocity; however, in the current data these signatures are completely absent at small energy losses and residues remain at large energy losses. At small energy losses the FDCSs are dominated by non-PCI higher-order effects.","PeriodicalId":20146,"journal":{"name":"Physical Review A","volume":"77 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142262921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Demonstration of superior communication through thermodynamically free channels in an optical quantum switch","authors":"Hao Tang, Yu Guo, Xiao-Min Hu, Yun-Feng Huang, Bi-Heng Liu, Chuan-Feng Li, Guang-Can Guo","doi":"10.1103/physreva.110.032422","DOIUrl":"https://doi.org/10.1103/physreva.110.032422","url":null,"abstract":"The release of the causal structure of physical events from a well-defined order to an indefinite order stimulates remarkable enhancements in various quantum information tasks. Some of these advantages, however, are questioned for the ambiguous role of the control system in the quantum switch, which is an experimentally realized process with an indefinite causal structure. In communications, for example, not only the superposition of alternative causal orders, but also the superposition of alternative trajectories can accelerate information transmissions. Here, we follow the proposal of Liu <i>et al.</i> [<span>Phys. Rev. Lett.</span> <b>129</b>, 230604 (2022)], and examine the information enhancement effect of indefinite causal orders with the toolkit of thermodynamics in a photonic platform. Specifically, we simulate the thermal interaction between a system qubit and two heat baths embedded in a quantum switch by implementing the corresponding switched thermal channels. Although its action on the system qubit only is thermally free, our results suggest that the quantum switch should be seen as a resource when the control qubit is also considered. Moreover, we characterize the non-Markovian property in this scenario by measuring the information backflows from the heat baths to the system qubit.","PeriodicalId":20146,"journal":{"name":"Physical Review A","volume":"48 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142262768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Probing the position-dependent optical energy fluence rate in three-dimensional scattering samples","authors":"Ozan Akdemir, Minh Duy Truong, Alfredo Rates, Ad Lagendijk, Willem L. Vos","doi":"10.1103/physreva.110.033520","DOIUrl":"https://doi.org/10.1103/physreva.110.033520","url":null,"abstract":"The accurate determination of the position-dependent energy fluence rate of scattered light (which is proportional to the energy density) is crucial to the understanding of transport in anisotropically scattering and absorbing samples, such as biological tissue, seawater, atmospheric turbulent layers, and light-emitting diodes. While Monte Carlo simulations are precise, their long computation time is not desirable. Common analytical approximations to the radiative transfer equation (RTE) fail to predict light transport and could even give unphysical results. Therefore, we experimentally probe the position-dependent energy fluence rate of light inside scattering samples where the widely used <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>P</mi><mn>1</mn></msub></math> and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>P</mi><mn>3</mn></msub></math> approximations to the RTE fail. The samples are three-dimensional (3D) aqueous suspensions of anisotropically scattering and both absorbing and nonabsorbing spherical scatterers, namely, microspheres (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>r</mi><mo>=</mo><mn>0.5</mn><mspace width=\"3.33333pt\"></mspace><mi>µ</mi><mi mathvariant=\"normal\">m</mi></mrow></math>) with and without absorbing dye. To probe the energy fluence rate, we detect the emission of quantum-dot reporter particles that are excited by the incident light and that are contained in a thin capillary. By scanning the capillary through the sample, we access the position dependence. We present a comprehensive discussion of experimental limitations and of both random and systematic errors. Our observations agree well with the Monte Carlo simulations and the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>P</mi><mn>3</mn></msub></math> approximation of the RTE with a correction for forward scattering. In contrast, the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>P</mi><mn>1</mn></msub></math> and the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>P</mi><mn>3</mn></msub></math> approximations deviate increasingly from our observations, ultimately even predicting unphysical negative energies.","PeriodicalId":20146,"journal":{"name":"Physical Review A","volume":"171 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142262919","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fundamental constants from photon-photon scattering in three-beam collisions","authors":"A. J. MacLeod, B. King","doi":"10.1103/physreva.110.032216","DOIUrl":"https://doi.org/10.1103/physreva.110.032216","url":null,"abstract":"Direct measurement of the elastic scattering of real photons on an electromagnetic field would allow the fundamental low-energy constants of quantum electrodynamics to be experimentally determined. We show that scenarios involving the collision of three laser beams have several advantages over conventional two-beam scenarios. The kinematics of a three-beam collision allows for a higher signal-to-background ratio in the detection region, without the need for polarimetry, and separates out contributions from different orders of photon scattering. A planar configuration of colliding a photon beam from an x-ray free-electron laser with two optical beams is studied in detail. We show that measurements of elastic photon scattering and vacuum birefringence are possible with currently available technology.","PeriodicalId":20146,"journal":{"name":"Physical Review A","volume":"3 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142262771","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reliable quantum memories with unreliable components","authors":"Anuj K. Nayak, Eric Chitambar, Lav R. Varshney","doi":"10.1103/physreva.110.032423","DOIUrl":"https://doi.org/10.1103/physreva.110.032423","url":null,"abstract":"Quantum memory systems are vital in quantum information processing for dependable storage and retrieval of quantum states. Inspired by classical reliability theories that synthesize reliable computing systems from unreliable components, we formalize the problem of reliable storage of quantum information using noisy components. We introduce the notion of stable quantum memories and define the storage rate as the ratio of the number of logical qubits to the total number of physical qubits as well as the circuit complexity of the decoder, which includes both quantum gates and measurements. We demonstrate that a strictly positive storage rate can be achieved by constructing a quantum memory system with quantum expander codes. Moreover, by reducing the reliable storage problem to reliable quantum communication, we provide upper bounds on the achievable storage capacity. In the case of physical qubits corrupted by noise satisfying hypercontractivity conditions, we provide a tighter upper bound on storage capacity using an entropy dissipation argument. Furthermore, observing that the time complexity of the decoder scales nontrivially with the number of physical qubits, achieving asymptotic rates may not be possible due to the induced dependence of the noise on the number of physical qubits. In this constrained nonasymptotic setting, we derive upper bounds on storage capacity using finite blocklength communication bounds. Finally, we numerically analyze the gap between upper and lower bounds in both asymptotic and nonasymptotic cases, and provide suggestions to tighten the gap.","PeriodicalId":20146,"journal":{"name":"Physical Review A","volume":"49 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142262767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Shallow-depth variational quantum hypothesis testing","authors":"Mahadevan Subramanian, Sai Vinjanampathy","doi":"10.1103/physreva.110.032424","DOIUrl":"https://doi.org/10.1103/physreva.110.032424","url":null,"abstract":"The task of discriminating between two known quantum channels is a well-known binary-hypothesis-testing task. We present a variational quantum algorithm with a parameterized state preparation and two-outcome positive operator-valued measure which defines the acceptance criteria for the hypothesis test. Both the state preparation and measurement are simultaneously optimized using the success probability of single-shot discrimination as an objective function which can be calculated using localized measurements. Under constrained signal-mode photon-number quantum illumination we match the performance of known optimal two-mode probes by simulating a bosonic circuit. Our results show that variational algorithms can prepare optimal states for binary hypothesis testing with resource constraints.","PeriodicalId":20146,"journal":{"name":"Physical Review A","volume":"51 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142262769","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of the chirp rate on single-shot coherent Rayleigh-Brillouin scattering","authors":"S. Suzuki, A. Gerakis, K. Hara","doi":"10.1103/physreva.110.033519","DOIUrl":"https://doi.org/10.1103/physreva.110.033519","url":null,"abstract":"Single-shot coherent Rayleigh-Brillouin scattering (CRBS) is modeled using direct simulation Monte Carlo (DSMC). In CRBS, an optical lattice generated by the interference of two pump lasers traps the neutral particles via the dipole force. The gradient of refractive index due to the trapped particles of the gaseous media leads to coherent scattering of a probe beam, resulting in the CRBS signal. Additionally, using a chirped laser beam, CRBS signals can be obtained in a single laser shot, shortening the measurement time of the gas flow (on the order of 100 ns). The DSMC results of single-shot CRBS assuming Maxwellian velocity distribution functions (VDFs) show good agreement with experimental data, including argon, carbon dioxide, and xenon, for different gas pressures. One of the key observations obtained from the present simulations is that the CRBS signals become asymmetric when using a fast chirp rate due to finite time for collisionless trapping and collisional thermalization.","PeriodicalId":20146,"journal":{"name":"Physical Review A","volume":"4 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142262776","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Swallow-tail dispersions of moving solitons in a two-dimensional fermionic superfluid","authors":"Jan Major, Joachim Brand","doi":"10.1103/physreva.110.033320","DOIUrl":"https://doi.org/10.1103/physreva.110.033320","url":null,"abstract":"Solitonlike localized wave solutions in a two-dimensional Fermi superfluid are studied by solving the Bogoliubov–de Gennes equations in the BCS regime of weak pairing interactions. The dispersion relations of these solitons are found to exhibit a peculiar swallow-tail shape, with cusps and multiple branches. The effective mass of the solitons is found to diverge and change sign at the cusp. This behavior is in contrast to the smooth dispersion relations and negative effective masses of solitons in the three-dimensional Fermi superfluid. The swallow-tail dispersion relations are shown to be a consequence of counterflow of the superfluid and sign-changing contributions to the superfluid current from different transverse momenta in the Bogoliubov–de Gennes formalism. The results are relevant for the understanding of solitonic excitations in two-dimensional Fermi superfluids, such as ultracold atomic gases and high-temperature superconductors.","PeriodicalId":20146,"journal":{"name":"Physical Review A","volume":"48 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142262775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Vacuum-polarization Wichmann-Kroll correction in the finite-basis-set approach","authors":"V. K. Ivanov, S. S. Baturin, D. A. Glazov, A. V. Volotka","doi":"10.1103/physreva.110.032815","DOIUrl":"https://doi.org/10.1103/physreva.110.032815","url":null,"abstract":"The finite-basis-set method is commonly used to calculate atomic spectra, including quantum electrodynamics contributions such as bound-electron self-energy. Still, it remains problematic and underexplored for vacuum-polarization calculations. We fill this gap by trying this approach in its application to the calculation of the vacuum-polarization charge density and the Wichmann-Kroll correction to the electron binding energy in a hydrogen-like ion. We study the convergence of the method with different types and sizes of basis sets. We cross-check our results for the Wichmann-Kroll correction by direct integration of the Green's function. As a relevant example, we consider several heavy hydrogen-like ions and evaluate the vacuum polarization correction for <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>S</mi></math> and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>P</mi></math> electron orbitals.","PeriodicalId":20146,"journal":{"name":"Physical Review A","volume":"19 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142262774","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}