Pub Date : 2024-07-03DOI: 10.1088/1367-2630/ad5c95
S Sarkar, F Ciccarello, A Carollo and A Bayat
Non-Hermitian (NH) physics predicts open quantum system dynamics with unique topological features such as exceptional points and the NH skin effect. We show that this new paradigm of topological systems can serve as probes for bulk Hamiltonian parameters with quantum-enhanced sensitivity reaching Heisenberg scaling. Such enhancement occurs close to a spectral topological phase transition, where the entire spectrum undergoes a delocalization transition. We provide an explanation for this enhanced sensitivity based on the closing of point gap, which is a genuinely NH energy gap with no Hermitian counterpart. This establishes a direct connection between energy-gap closing and quantum enhancement in the NH realm. Our findings are demonstrated through several paradigmatic NH topological models in various dimensions and potential experimental implementations.
{"title":"Critical non-Hermitian topology induced quantum sensing","authors":"S Sarkar, F Ciccarello, A Carollo and A Bayat","doi":"10.1088/1367-2630/ad5c95","DOIUrl":"https://doi.org/10.1088/1367-2630/ad5c95","url":null,"abstract":"Non-Hermitian (NH) physics predicts open quantum system dynamics with unique topological features such as exceptional points and the NH skin effect. We show that this new paradigm of topological systems can serve as probes for bulk Hamiltonian parameters with quantum-enhanced sensitivity reaching Heisenberg scaling. Such enhancement occurs close to a spectral topological phase transition, where the entire spectrum undergoes a delocalization transition. We provide an explanation for this enhanced sensitivity based on the closing of point gap, which is a genuinely NH energy gap with no Hermitian counterpart. This establishes a direct connection between energy-gap closing and quantum enhancement in the NH realm. Our findings are demonstrated through several paradigmatic NH topological models in various dimensions and potential experimental implementations.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"38 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141550479","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}
Pub Date : 2024-07-02DOI: 10.1088/1367-2630/ad59ff
P C Sreeparvathy, Rovi Angelo B Villaos, Zhi-Quan Huang and Feng-Chuan Chuang
Higher-order topological insulators hosting intriguing topologically protected hinge or corner states are of significant research interest. However, materials that possess higher-order topological hinge states associated with gapless bulk Dirac phases still need to be explored. Using first-principles calculations with hybrid exchange functional, we explore the electronic structure and topological properties of Y3InC and a few of its sister compounds, totaling 16 bulk materials. A symmetry-protected triple point phase, with dominated d-t2g character, is observed in Y3InC without spin–orbit coupling (SOC). Interestingly, the SOC induces a twin Dirac node phase in the bulk Y3InC. Furthermore, the computed Z4 topological invariant reveals the higher-order topological nature of investigated materials. To demonstrate the gapless hinge states, we conduct edge state calculations using a rod-shaped geometry of Y3InC. Remarkably, Y3InC is identified to host multi-Dirac nodes in the bulk and surface phases together with the higher-order hinge states. These results lay the groundwork for further experimental and theoretical investigations into cubic antiperovskite materials for higher-order topological phases.
{"title":"Higher-order topological Dirac phase in Y3InC: a first-principles study","authors":"P C Sreeparvathy, Rovi Angelo B Villaos, Zhi-Quan Huang and Feng-Chuan Chuang","doi":"10.1088/1367-2630/ad59ff","DOIUrl":"https://doi.org/10.1088/1367-2630/ad59ff","url":null,"abstract":"Higher-order topological insulators hosting intriguing topologically protected hinge or corner states are of significant research interest. However, materials that possess higher-order topological hinge states associated with gapless bulk Dirac phases still need to be explored. Using first-principles calculations with hybrid exchange functional, we explore the electronic structure and topological properties of Y3InC and a few of its sister compounds, totaling 16 bulk materials. A symmetry-protected triple point phase, with dominated d-t2g character, is observed in Y3InC without spin–orbit coupling (SOC). Interestingly, the SOC induces a twin Dirac node phase in the bulk Y3InC. Furthermore, the computed Z4 topological invariant reveals the higher-order topological nature of investigated materials. To demonstrate the gapless hinge states, we conduct edge state calculations using a rod-shaped geometry of Y3InC. Remarkably, Y3InC is identified to host multi-Dirac nodes in the bulk and surface phases together with the higher-order hinge states. These results lay the groundwork for further experimental and theoretical investigations into cubic antiperovskite materials for higher-order topological phases.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"47 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141518416","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}
Pub Date : 2024-07-02DOI: 10.1088/1367-2630/ad50ff
Gennaro Tucci, Ramin Golestanian and Suropriya Saha
A multicomponent mixture of Janus colloids with distinct catalytic coats and phoretic mobilities is a promising theoretical system to explore the collective behavior arising from nonreciprocal interactions. An active colloid produces (or consumes) chemicals, self-propels, drifts along chemical gradients, and rotates its intrinsic polarity to align with a gradient. As a result the connection from microscopics to continuum theories through coarse-graining couples densities and polarization fields in unique ways. Focusing on a binary mixture, we show that these couplings render the unpatterned reference state unstable to small perturbations through a variety of instabilities including oscillatory ones which arise on crossing an exceptional point or through a Hopf bifurcation. For fast relaxation of the polar fields, they can be eliminated in favor of the density fields to obtain a microscopic realization of the Nonreciprocal Cahn–Hilliard model for two conserved species with two distinct sources of non-reciprocity, one in the interaction coefficient and the other in the interfacial tension. Our work establishes Janus colloids as a versatile model for a bottom-up approach to both scalar and polar active mixtures.
{"title":"Nonreciprocal collective dynamics in a mixture of phoretic Janus colloids","authors":"Gennaro Tucci, Ramin Golestanian and Suropriya Saha","doi":"10.1088/1367-2630/ad50ff","DOIUrl":"https://doi.org/10.1088/1367-2630/ad50ff","url":null,"abstract":"A multicomponent mixture of Janus colloids with distinct catalytic coats and phoretic mobilities is a promising theoretical system to explore the collective behavior arising from nonreciprocal interactions. An active colloid produces (or consumes) chemicals, self-propels, drifts along chemical gradients, and rotates its intrinsic polarity to align with a gradient. As a result the connection from microscopics to continuum theories through coarse-graining couples densities and polarization fields in unique ways. Focusing on a binary mixture, we show that these couplings render the unpatterned reference state unstable to small perturbations through a variety of instabilities including oscillatory ones which arise on crossing an exceptional point or through a Hopf bifurcation. For fast relaxation of the polar fields, they can be eliminated in favor of the density fields to obtain a microscopic realization of the Nonreciprocal Cahn–Hilliard model for two conserved species with two distinct sources of non-reciprocity, one in the interaction coefficient and the other in the interfacial tension. Our work establishes Janus colloids as a versatile model for a bottom-up approach to both scalar and polar active mixtures.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"151 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141518415","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}
Pub Date : 2024-07-02DOI: 10.1088/1367-2630/ad5b7f
Jie Chen, Maobin Hu and Jinde Cao
In the contemporary era, the advent of epidemics instigates a substantial upswing in relevant information dissemination, bolstering individuals’ resistance to infection by concurrently reducing activity contacts and reinforcing personal protective measures. To elucidate this intricate dynamics, we introduce a composite four-layer network model designed to capture the interplay among information-driven awareness, human activity, and epidemic spread, with a focus on the allocation of individuals’ limited attention in diminishing activity frequency and self-infection rates. One intriguing observation from our findings is an anomalous, concave non-monotonic relationship between awareness trade-off and epidemic spread, with a more pronounced prevalence at an intermediate least awareness efficacy. This underscores the inadvisability of relaxing self-protection through reduced activity frequency or compensating for increased activity frequency by enhancing self-protection. Especially noteworthy is the significance of enhancing self-protection in response to heightened information dissemination and inherent activity demands to curtail infection risk. However, in scenarios with increasing ancillary activity frequency, the emphasis should exclusively shift towards reducing activity exposure. The model establishes a theoretical threshold for accurately predicting awareness efficacy in epidemic outbreaks. Optimal awareness allocation consistently resides at the extremes—either completely avoiding unnecessary activity contact or adopting full self-protection. This guidance, contingent on information level and activity demand, offers valuable insights into the delicate balance between individual behaviors and epidemic prevention.
{"title":"Optimizing information-driven awareness allocation for controlling activity-triggered epidemic spread","authors":"Jie Chen, Maobin Hu and Jinde Cao","doi":"10.1088/1367-2630/ad5b7f","DOIUrl":"https://doi.org/10.1088/1367-2630/ad5b7f","url":null,"abstract":"In the contemporary era, the advent of epidemics instigates a substantial upswing in relevant information dissemination, bolstering individuals’ resistance to infection by concurrently reducing activity contacts and reinforcing personal protective measures. To elucidate this intricate dynamics, we introduce a composite four-layer network model designed to capture the interplay among information-driven awareness, human activity, and epidemic spread, with a focus on the allocation of individuals’ limited attention in diminishing activity frequency and self-infection rates. One intriguing observation from our findings is an anomalous, concave non-monotonic relationship between awareness trade-off and epidemic spread, with a more pronounced prevalence at an intermediate least awareness efficacy. This underscores the inadvisability of relaxing self-protection through reduced activity frequency or compensating for increased activity frequency by enhancing self-protection. Especially noteworthy is the significance of enhancing self-protection in response to heightened information dissemination and inherent activity demands to curtail infection risk. However, in scenarios with increasing ancillary activity frequency, the emphasis should exclusively shift towards reducing activity exposure. The model establishes a theoretical threshold for accurately predicting awareness efficacy in epidemic outbreaks. Optimal awareness allocation consistently resides at the extremes—either completely avoiding unnecessary activity contact or adopting full self-protection. This guidance, contingent on information level and activity demand, offers valuable insights into the delicate balance between individual behaviors and epidemic prevention.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"230 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141518417","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}
Pub Date : 2024-07-01DOI: 10.1088/1367-2630/ad5906
S Süleyman Kahraman, Kelvin Titimbo, Zhe He, Jung-Tsung Shen and Lihong V Wang
The multi-stage Stern–Gerlach experiment conducted by Frisch and Segrè includes two cascaded quantum measurements with a nonadiabatic flipper in between. The Frisch and Segrè experiment has been modeled analytically by Majorana without the nuclear effect and subsequently revised by Rabi with the hyperfine interaction. However, the theoretical predictions do not match the experimental observation accurately. Here, we numerically solve the standard quantum mechanical model, via the von Neumann equation, including the hyperfine interaction for the time evolution of the spin. Thus far, the coefficients of determination from the standard quantum mechanical model without using free parameters are still low, indicating a mismatch between the theory and the experiment. Non-standard variants that improve the match are explored for discussion.
{"title":"Quantum mechanical modeling of the multi-stage Stern–Gerlach experiment conducted by Frisch and Segrè","authors":"S Süleyman Kahraman, Kelvin Titimbo, Zhe He, Jung-Tsung Shen and Lihong V Wang","doi":"10.1088/1367-2630/ad5906","DOIUrl":"https://doi.org/10.1088/1367-2630/ad5906","url":null,"abstract":"The multi-stage Stern–Gerlach experiment conducted by Frisch and Segrè includes two cascaded quantum measurements with a nonadiabatic flipper in between. The Frisch and Segrè experiment has been modeled analytically by Majorana without the nuclear effect and subsequently revised by Rabi with the hyperfine interaction. However, the theoretical predictions do not match the experimental observation accurately. Here, we numerically solve the standard quantum mechanical model, via the von Neumann equation, including the hyperfine interaction for the time evolution of the spin. Thus far, the coefficients of determination from the standard quantum mechanical model without using free parameters are still low, indicating a mismatch between the theory and the experiment. Non-standard variants that improve the match are explored for discussion.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"82 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141518418","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}
Pub Date : 2024-06-30DOI: 10.1088/1367-2630/ad5752
Lukas Beringer, Mathias Steinhuber, Juan Diego Urbina, Klaus Richter and Steven Tomsovic
This work develops a quantum control application of many-body quantum chaos for ultracold bosonic gases trapped in optical lattices. It is long known how to harness exponential sensitivity to changes in initial conditions for control purposes in classically chaotic systems. In the technique known as targeting, instead of a hindrance to control, the instability becomes a resource. Recently, this classical targeting has been generalized to quantum systems either by periodically countering the inevitable quantum state spreading or by introducing a control Hamiltonian, where both enable localized states to be guided along special chaotic trajectories toward any of a broad variety of desired target states. Only strictly unitary dynamics are involved; i.e. it gives a coherent quantum targeting. In this paper, the introduction of a control Hamiltonian is applied to Bose–Hubbard systems in chaotic dynamical regimes. Properly selected unstable mean field solutions can be followed particularly rapidly to states possessing precise phase relationships and occupancies. In essence, the method generates a quantum simulation technique that can access rather special states. The protocol reduces to a time-dependent control of the chemical potentials, opening up the possibility for application in optical lattice experiments. Explicit applications to custom state preparation and stabilization of quantum many-body scars are presented in one- and two-dimensional lattices (three-dimensional applications are similarly possible).
{"title":"Controlling many-body quantum chaos: Bose–Hubbard systems","authors":"Lukas Beringer, Mathias Steinhuber, Juan Diego Urbina, Klaus Richter and Steven Tomsovic","doi":"10.1088/1367-2630/ad5752","DOIUrl":"https://doi.org/10.1088/1367-2630/ad5752","url":null,"abstract":"This work develops a quantum control application of many-body quantum chaos for ultracold bosonic gases trapped in optical lattices. It is long known how to harness exponential sensitivity to changes in initial conditions for control purposes in classically chaotic systems. In the technique known as targeting, instead of a hindrance to control, the instability becomes a resource. Recently, this classical targeting has been generalized to quantum systems either by periodically countering the inevitable quantum state spreading or by introducing a control Hamiltonian, where both enable localized states to be guided along special chaotic trajectories toward any of a broad variety of desired target states. Only strictly unitary dynamics are involved; i.e. it gives a coherent quantum targeting. In this paper, the introduction of a control Hamiltonian is applied to Bose–Hubbard systems in chaotic dynamical regimes. Properly selected unstable mean field solutions can be followed particularly rapidly to states possessing precise phase relationships and occupancies. In essence, the method generates a quantum simulation technique that can access rather special states. The protocol reduces to a time-dependent control of the chemical potentials, opening up the possibility for application in optical lattice experiments. Explicit applications to custom state preparation and stabilization of quantum many-body scars are presented in one- and two-dimensional lattices (three-dimensional applications are similarly possible).","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"132 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141518420","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}
Pub Date : 2024-06-30DOI: 10.1088/1367-2630/ad59bb
Lennart Binkowski, Gereon Koßmann, Timo Ziegler and René Schwonnek
The quantum alternating operator ansatz (QAOA) and its predecessor, the quantum approximate optimization algorithm, are one of the most widely used quantum algorithms for solving combinatorial optimization problems. However, as there is yet no rigorous proof of convergence for the QAOA, we provide one in this paper. The proof involves retracing the connection between the quantum adiabatic algorithm and the QAOA, and naturally suggests a refined definition of the ‘phase separator’ and ‘mixer’ keywords.
{"title":"Elementary proof of QAOA convergence","authors":"Lennart Binkowski, Gereon Koßmann, Timo Ziegler and René Schwonnek","doi":"10.1088/1367-2630/ad59bb","DOIUrl":"https://doi.org/10.1088/1367-2630/ad59bb","url":null,"abstract":"The quantum alternating operator ansatz (QAOA) and its predecessor, the quantum approximate optimization algorithm, are one of the most widely used quantum algorithms for solving combinatorial optimization problems. However, as there is yet no rigorous proof of convergence for the QAOA, we provide one in this paper. The proof involves retracing the connection between the quantum adiabatic algorithm and the QAOA, and naturally suggests a refined definition of the ‘phase separator’ and ‘mixer’ keywords.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"17 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141518421","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}
Pub Date : 2024-06-30DOI: 10.1088/1367-2630/ad5464
Yigal Ilin and Itai Arad
We present a scalable method for learning local quantum channels using local expectation values measured on a single state—their steady state. Our method is inspired by the algorithms for learning local Hamiltonians from their ground states. For it to succeed, the steady state must be non-trivial, and therefore the channel needs to be non-unital. Such non-unital channels are readily implementable on present day quantum computers using mid-circuit measurements or RESET gates. We demonstrate that the full structure of such channels is encoded in their steady states, and can be learned efficiently using only the expectation values of local observables on these states. We emphasize two immediate applications to illustrate our approach: (i) Using engineered dissipative dynamics, we offer a straightforward way to assess the accuracy of a given noise model in a regime where all qubits are actively utilized for a significant duration. (ii) Given a parameterized noise model for the entire system, our method can learn its underlying parameters. We demonstrate both applications using numerical simulations and experimental trials conducted on an IBMQ machine.
{"title":"Learning a quantum channel from its steady-state","authors":"Yigal Ilin and Itai Arad","doi":"10.1088/1367-2630/ad5464","DOIUrl":"https://doi.org/10.1088/1367-2630/ad5464","url":null,"abstract":"We present a scalable method for learning local quantum channels using local expectation values measured on a single state—their steady state. Our method is inspired by the algorithms for learning local Hamiltonians from their ground states. For it to succeed, the steady state must be non-trivial, and therefore the channel needs to be non-unital. Such non-unital channels are readily implementable on present day quantum computers using mid-circuit measurements or RESET gates. We demonstrate that the full structure of such channels is encoded in their steady states, and can be learned efficiently using only the expectation values of local observables on these states. We emphasize two immediate applications to illustrate our approach: (i) Using engineered dissipative dynamics, we offer a straightforward way to assess the accuracy of a given noise model in a regime where all qubits are actively utilized for a significant duration. (ii) Given a parameterized noise model for the entire system, our method can learn its underlying parameters. We demonstrate both applications using numerical simulations and experimental trials conducted on an IBMQ machine.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"14 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141518419","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}
Pub Date : 2024-06-27DOI: 10.1088/1367-2630/ad5a61
Giuseppe De Riso, Francesco Cipriani, Lorenzo Villani, Vincenzo Bisogno, Marco Lo Schiavo, Alfonso Romano and Canio Noce
We present a detailed analysis and optimization of the variational quantum algorithms required to find the ground state of a correlated electron model, using several types of variational ansatz. Specifically, we apply our approach to the atomic limit of the Anderson model, which is widely studied in condensed matter physics since it can simulate fundamental physical phenomena, ranging from magnetism to superconductivity. The method is developed by presenting efficient state preparation circuits that exhibit total spin, spin projection, particle number and time-reversal symmetries. These states contain the minimal number of variational parameters needed to fully span the appropriate symmetry subspace allowing to avoid irrelevant sectors of Hilbert space. Then, we show how to construct quantum circuits, providing explicit decomposition and gate count in terms of standard gate sets. We test these quantum algorithms looking at ideal quantum computer simulations as well as implementing quantum noisy simulations. We finally perform an accurate comparative analysis among the approaches implemented, highlighting their merits and shortcomings.
{"title":"Ansatz optimization of the variational quantum eigensolver tested on the atomic Anderson model","authors":"Giuseppe De Riso, Francesco Cipriani, Lorenzo Villani, Vincenzo Bisogno, Marco Lo Schiavo, Alfonso Romano and Canio Noce","doi":"10.1088/1367-2630/ad5a61","DOIUrl":"https://doi.org/10.1088/1367-2630/ad5a61","url":null,"abstract":"We present a detailed analysis and optimization of the variational quantum algorithms required to find the ground state of a correlated electron model, using several types of variational ansatz. Specifically, we apply our approach to the atomic limit of the Anderson model, which is widely studied in condensed matter physics since it can simulate fundamental physical phenomena, ranging from magnetism to superconductivity. The method is developed by presenting efficient state preparation circuits that exhibit total spin, spin projection, particle number and time-reversal symmetries. These states contain the minimal number of variational parameters needed to fully span the appropriate symmetry subspace allowing to avoid irrelevant sectors of Hilbert space. Then, we show how to construct quantum circuits, providing explicit decomposition and gate count in terms of standard gate sets. We test these quantum algorithms looking at ideal quantum computer simulations as well as implementing quantum noisy simulations. We finally perform an accurate comparative analysis among the approaches implemented, highlighting their merits and shortcomings.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"14 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141507956","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}
Pub Date : 2024-06-26DOI: 10.1088/1367-2630/ad5a31
Yong Cao, Lijuan Sheng, Qiang Zhou, Rong Wang, Zhenkuan Chen and Xiaohui Ling
Photonic spin Hall effect (PSHE) in chiral PT-symmetric systems exhibits many exotic features, but the underlying physical mechanism has not been well elucidated. Here, through rigorous calculations based on full-wave theory, we reveal the physical mechanism of the exotic PSHE and identify a chirality-enabled topological phase transition. When circularly polarized light is incident on a chiral PT-symmetric system, the transmitted beam contains two components: a spin-flipped abnormal mode that acquires a geometric phase (exhibiting a vortex or a spin-Hall shift), and a spin-maintained normal mode that does not exhibit such a phase. If the phase difference between the cross-polarized Fresnel coefficients cannot be ignored, it results in a chirality-enabled phase and intensity distribution in the abnormal mode, which induces an exotic PSHE. Consequently, as the incident angle increases, a chirality-induced topological phase transition occurs, namely the transition from the vortex generation to the exotic PSHE. Finally, we confirm that the asymmetric and periodic PSHE in the chiral slab is also related to the phase difference between the cross-polarized Fresnel coefficients. These concepts and findings also provide an opportunity for unifying the phenomena of topological phase transitions in various spin-orbit photonic systems.
{"title":"Chirality-enabled topological phase transitions in parity-time symmetric systems","authors":"Yong Cao, Lijuan Sheng, Qiang Zhou, Rong Wang, Zhenkuan Chen and Xiaohui Ling","doi":"10.1088/1367-2630/ad5a31","DOIUrl":"https://doi.org/10.1088/1367-2630/ad5a31","url":null,"abstract":"Photonic spin Hall effect (PSHE) in chiral PT-symmetric systems exhibits many exotic features, but the underlying physical mechanism has not been well elucidated. Here, through rigorous calculations based on full-wave theory, we reveal the physical mechanism of the exotic PSHE and identify a chirality-enabled topological phase transition. When circularly polarized light is incident on a chiral PT-symmetric system, the transmitted beam contains two components: a spin-flipped abnormal mode that acquires a geometric phase (exhibiting a vortex or a spin-Hall shift), and a spin-maintained normal mode that does not exhibit such a phase. If the phase difference between the cross-polarized Fresnel coefficients cannot be ignored, it results in a chirality-enabled phase and intensity distribution in the abnormal mode, which induces an exotic PSHE. Consequently, as the incident angle increases, a chirality-induced topological phase transition occurs, namely the transition from the vortex generation to the exotic PSHE. Finally, we confirm that the asymmetric and periodic PSHE in the chiral slab is also related to the phase difference between the cross-polarized Fresnel coefficients. These concepts and findings also provide an opportunity for unifying the phenomena of topological phase transitions in various spin-orbit photonic systems.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"27 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141507957","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}
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