Quantum最新文献_第4页

Multipartite entanglement distribution in a topological photonic network

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-02-10 DOI: 10.22331/q-2025-02-10-1625

Juan Zurita, Andrés Agustí Casado, Charles E. Creffield, Gloria Platero

引用次数: 0

Efficient Hamiltonian encoding algorithms for extracting quantum control mechanism as interfering pathway amplitudes in the Dyson series

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-02-10 DOI: 10.22331/q-2025-02-10-1626

Erez Abrams, Michael Kasprzak, Gaurav Bhole, Tak-San Ho, Herschel Rabitz

{"title":"Efficient Hamiltonian encoding algorithms for extracting quantum control mechanism as interfering pathway amplitudes in the Dyson series","authors":"Erez Abrams, Michael Kasprzak, Gaurav Bhole, Tak-San Ho, Herschel Rabitz","doi":"10.22331/q-2025-02-10-1626","DOIUrl":"https://doi.org/10.22331/q-2025-02-10-1626","url":null,"abstract":"Hamiltonian encoding is a methodology for revealing the mechanism behind the dynamics governing controlled quantum systems. In this paper, following Mitra and Rabitz [9], we define mechanism via pathways of eigenstates that describe the evolution of the system, where each pathway is associated with a complex-valued amplitude corresponding to a term in the Dyson series. The evolution of the system is determined by the constructive and destructive interference of these pathway amplitudes. Pathways with similar attributes can be grouped together into pathway classes. The amplitudes of pathway classes are computed by modulating the Hamiltonian matrix elements and decoding the subsequent evolution of the system rather than by direct computation of the individual terms in the Dyson series. The original implementation of Hamiltonian encoding was computationally intensive and became prohibitively expensive in large quantum systems. This paper presents two new encoding algorithms that calculate the amplitudes of pathway classes by using techniques from graph theory and algebraic topology to exploit patterns in the set of allowed transitions, greatly reducing the number of matrix elements that need to be modulated. These new algorithms provide an exponential decrease in both computation time and memory utilization with respect to the Hilbert space dimension of the system. To demonstrate the use of these techniques, they are applied to two illustrative state-to-state transition problems.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"85 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143375501","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}

引用次数: 0

Comparative study of quantum error correction strategies for the heavy-hexagonal lattice

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-02-06 DOI: 10.22331/q-2025-02-06-1623

César Benito, Esperanza López, Borja Peropadre, Alejandro Bermudez

{"title":"Comparative study of quantum error correction strategies for the heavy-hexagonal lattice","authors":"César Benito, Esperanza López, Borja Peropadre, Alejandro Bermudez","doi":"10.22331/q-2025-02-06-1623","DOIUrl":"https://doi.org/10.22331/q-2025-02-06-1623","url":null,"abstract":"Topological quantum error correction is a milestone in the scaling roadmap of quantum computers, which targets circuits with trillions of gates that would allow running quantum algorithms for real-world problems. The square-lattice surface code has become the workhorse to address this challenge, as it poses milder requirements on current devices both in terms of required error rates and small local connectivities. In some platforms, however, the connectivities are kept even lower in order to minimise gate errors at the hardware level, which limits the error correcting codes that can be directly implemented on them. In this work, we make a comparative study of possible strategies to overcome this limitation for the heavy-hexagonal lattice, the architecture of current IBM superconducting quantum computers. We explore two complementary strategies: the search for an efficient embedding of the surface code into the heavy-hexagonal lattice, as well as the use of codes whose connectivity requirements are naturally tailored to this architecture, such as subsystem-type and Floquet codes. Using noise models of increased complexity, we assess the performance of these strategies for IBM devices in terms of their error thresholds and qubit footprints. An optimized SWAP-based embedding of the surface code is found to be the most promising strategy towards a near-term demonstration of quantum error correction advantage.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"11 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143192296","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}

引用次数: 0

Enhancing Scalability of Quantum Eigenvalue Transformation of Unitary Matrices for Ground State Preparation through Adaptive Finer Filtering

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-02-06 DOI: 10.22331/q-2025-02-06-1624

Erenay Karacan, Yanbin Chen, Christian B. Mendl

{"title":"Enhancing Scalability of Quantum Eigenvalue Transformation of Unitary Matrices for Ground State Preparation through Adaptive Finer Filtering","authors":"Erenay Karacan, Yanbin Chen, Christian B. Mendl","doi":"10.22331/q-2025-02-06-1624","DOIUrl":"https://doi.org/10.22331/q-2025-02-06-1624","url":null,"abstract":"Hamiltonian simulation is a domain where quantum computers have the potential to outperform their classical counterparts. One of the main challenges of such quantum algorithms is increasing the system size, which is necessary to achieve meaningful quantum advantage. In this work, we present an approach to improve the scalability of eigenspace filtering for the ground state preparation of a given Hamiltonian. Our method aims to tackle limitations introduced by a small spectral gap and high degeneracy of low energy states. It is based on an adaptive sequence of eigenspace filtering through Quantum Eigenvalue Transformation of Unitary Matrices (QETU) combined with spectrum profiling. By combining our proposed algorithm with state-of-the-art phase estimation methods, we achieved good approximations for the ground state energy with local, two-qubit gate depolarizing probability up to $10^{-4}$. To demonstrate the key results in this work, we ran simulations with the transverse-field Ising Model on classical computers using $texttt{Qiskit}$. We compare the performance of our approach with the static implementation of QETU and show that we can consistently achieve three to four orders of magnitude improvement in the absolute error rate.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"40 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143191974","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}

引用次数: 0

Theory of Multimode Squeezed Light Generation in Lossy Media

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-02-04 DOI: 10.22331/q-2025-02-04-1621

Denis A. Kopylov, Torsten Meier, Polina R. Sharapova

引用次数: 0

Metrological Advantages in Seeded and Lossy Nonlinear Interferometers

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-02-04 DOI: 10.22331/q-2025-02-04-1619

Jasper Kranias, Guillaume Thekkadath, Khabat Heshami, Aaron Z. Goldberg

引用次数: 0

Tight bounds for antidistinguishability and circulant sets of pure quantum states

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-02-04 DOI: 10.22331/q-2025-02-04-1622

Nathaniel Johnston, Vincent Russo, Jamie Sikora

引用次数: 0

Low-Rank Variational Quantum Algorithm for the Dynamics of Open Quantum Systems

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-02-04 DOI: 10.22331/q-2025-02-04-1620

Sara Santos, Xinyu Song, Vincenzo Savona

{"title":"Low-Rank Variational Quantum Algorithm for the Dynamics of Open Quantum Systems","authors":"Sara Santos, Xinyu Song, Vincenzo Savona","doi":"10.22331/q-2025-02-04-1620","DOIUrl":"https://doi.org/10.22331/q-2025-02-04-1620","url":null,"abstract":"The simulation of many-body open quantum systems is key to solving numerous outstanding problems in physics, chemistry, material science, and in the development of quantum technologies. Near-term quantum computers may bring considerable advantage for the efficient simulation of their static and dynamical properties, thanks to hybrid quantum-classical variational algorithms to approximate the dynamics of the density matrix describing the quantum state in terms of an ensemble average. Here, a variational quantum algorithm is developed to simulate the real-time evolution of the density matrix governed by the Lindblad master equation, under the assumption that the quantum state has a bounded entropy along the dynamics, entailing a low-rank representation of its density matrix. The algorithm encodes each pure state of the statistical mixture as a parametrized quantum circuit, and the associated probabilities as additional variational parameters stored classically, thereby requiring a significantly lower number of qubits than algorithms where the full density matrix is encoded in the quantum memory. Two variational ansatze are proposed, and their effectiveness is assessed in the simulation of the dynamics of a 2D dissipative transverse field Ising model. The results underscore the algorithm's efficiency in simulating the dynamics of open quantum systems in the low-rank regime with limited quantum resources on a near-term quantum device.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"38 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143124857","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}

引用次数: 0

Measurement events relative to temporal quantum reference frames

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-01-30 DOI: 10.22331/q-2025-01-30-1616

Ladina Hausmann, Alexander Schmidhuber, Esteban Castro-Ruiz

{"title":"Measurement events relative to temporal quantum reference frames","authors":"Ladina Hausmann, Alexander Schmidhuber, Esteban Castro-Ruiz","doi":"10.22331/q-2025-01-30-1616","DOIUrl":"https://doi.org/10.22331/q-2025-01-30-1616","url":null,"abstract":"The Page-Wootters formalism is a proposal for reconciling the background-dependent, quantum-mechanical notion of time with the background independence of general relativity. However, the physical meaning of this framework remains debated. In this work, we compare two consistent approaches to the Page-Wootters formalism to clarify the operational meaning of evolution and measurements with respect to a temporal quantum reference frame. The so-called \"twirled observable\" approach implements measurements as operators that are invariant with respect to the Hamiltonian constraint. The \"purified measurement\" approach instead models measurements dynamically by modifying the constraint itself. While both approaches agree in the limit of ideal clocks, a natural generalization of the purified measurement approach to the case of non-ideal, finite-resource clocks yields a radically different picture. We discuss the physical origin of this discrepancy and argue that these approaches describe operationally distinct situations. Moreover, we show that, for non-ideal clocks, the purified measurement approach yields a time non-local evolution equation, which can lead to non-unitary evolution. Moreover, it implies a fundamental limitation to the operational definition of the temporal order of events. Nevertheless, unitarity and definite temporal order can be restored if we assume that time is discrete.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"23 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143056221","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}

引用次数: 0

Fundamental charges for dual-unitary circuits

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-01-30 DOI: 10.22331/q-2025-01-30-1615

Tom Holden-Dye, Lluis Masanes, Arijeet Pal

{"title":"Fundamental charges for dual-unitary circuits","authors":"Tom Holden-Dye, Lluis Masanes, Arijeet Pal","doi":"10.22331/q-2025-01-30-1615","DOIUrl":"https://doi.org/10.22331/q-2025-01-30-1615","url":null,"abstract":"Dual-unitary quantum circuits have recently attracted attention as an analytically tractable model of many-body quantum dynamics. Consisting of a 1+1D lattice of 2-qudit gates arranged in a 'brickwork' pattern, these models are defined by the constraint that each gate must remain unitary under swapping the roles of space and time. This dual-unitarity restricts the dynamics of local operators in these circuits: the support of any such operator must grow at the effective speed of light of the system, along one or both of the edges of a causal light cone set by the geometry of the circuit. Using this property, it is shown here that for 1+1D dual-unitary circuits the set of width-$w$ conserved densities (constructed from operators supported over $w$ consecutive sites) is in one-to-one correspondence with the set of width-$w$ solitons – operators which, up to a multiplicative phase, are simply spatially translated at the effective speed of light by the dual-unitary dynamics. A number of ways to construct these many-body solitons (explicitly in the case where the local Hilbert space dimension $d=2$) are then demonstrated: firstly, via a simple construction involving products of smaller, constituent solitons; and secondly, via a construction which cannot be understood as simply in terms of products of smaller solitons, but which does have a neat interpretation in terms of products of fermions under a Jordan-Wigner transformation. This provides partial progress towards a characterisation of the microscopic structure of complex many-body solitons (in dual-unitary circuits on qubits), whilst also establishing a link between fermionic models and dual-unitary circuits, advancing our understanding of what kinds of physics can be explored in this framework.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"20 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143056964","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}

引用次数: 0