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We develop randomized quantum algorithms to simulate quantum collision models, also known as repeated interaction schemes, which provide a rich framework to model various open-system dynamics. The underlying technique involves composing…

Quantum Physics · Physics 2025-08-20 Kushagra Garg , Zeeshan Ahmed , Subhadip Mitra , Shantanav Chakraborty

The control over quantum states in atomic systems has led to the most precise optical atomic clocks to date. Their sensitivity is currently bounded by the standard quantum limit, a fundamental floor set by quantum mechanics for uncorrelated…

Quantum sensing and metrology present one of the most promising near-term applications in the field of quantum technologies, with quantum sensors enabling unprecedented precision in measurements of electric, magnetic or gravitational fields…

Quantum computing allows for the manipulation of highly correlated states whose properties quickly go beyond the capacity of any classical method to calculate. Thus one natural problem which could lend itself to quantum advantage is the…

Quantum Physics · Physics 2024-12-19 Kevin Lively , Tim Bode , Jochen Szangolies , Jian-Xin Zhu , Benedikt Fauseweh

We summarise important recent advances in quantum metrology, in connection to experiments in cold gases, trapped cold atoms and photons. First we review simple metrological setups, such as quantum metrology with spin squeezed states, with…

Quantum Physics · Physics 2015-01-27 Geza Toth , Iagoba Apellaniz

Quantum entanglement can provide enhanced precision beyond standard quantum limit (SQL), the highest precision achievable with classical means. It remains challenging, however, to observe large enhancement limited by the experimental…

Quantum Gases · Physics 2022-12-20 Tian-Wei Mao , Qi Liu , Xin-Wei Li , Jia-Hao Cao , Feng Chen , Wen-Xin Xu , Meng Khoon Tey , Yi-Xiao Huang , Li You

Many-body quantum chaos has immense potential as a tool to accelerate the preparation of entangled states and overcome challenges due to decoherence and technical noise. Here, we study how chaos in the paradigmatic Dicke model, which…

Quantum Gases · Physics 2024-10-08 Yicheng Zhang , Juan Zuniga Castro , Robert J. Lewis-Swan

We argue that it is possible in principle to reduce the uncertainty of an atomic magnetometer by double-passing a far-detuned laser field through the atomic sample as it undergoes Larmor precession. Numerical simulations of the quantum…

Quantum Physics · Physics 2009-06-17 Bradley A. Chase , Ben Q. Baragiola , Heather L. Partner , Brigette D. Black , JM Geremia

We significantly enhance the simulation accuracy of initial Trotter circuits for Hamiltonian simulation of quantum systems by integrating first-order Riemannian optimization with tensor network methods. Unlike previous approaches, our…

Quantum Physics · Physics 2025-12-30 Isabel Nha Minh Le , Shuo Sun , Christian B. Mendl

Quantum computing and quantum sensing represent two distinct frontiers of quantum information science. In this work, we harness quantum computing to solve a fundamental and practically important sensing problem: the detection of weak…

Quantum Physics · Physics 2025-01-15 Richard R. Allen , Francisco Machado , Isaac L. Chuang , Hsin-Yuan Huang , Soonwon Choi

We propose a method for Hamiltonian engineering in quantum information processing architectures that requires no local control, but only relies on collective qubit rotations and field gradients. The technique achieves a spatial modulation…

Quantum Physics · Physics 2013-06-12 Ashok Ajoy , Paola Cappellaro

The passive states of a quantum system minimize the average energy among all the states with a given spectrum. We prove that passive states are the optimal inputs of single-jump lossy quantum channels. These channels arise from a weak…

Quantum Physics · Physics 2016-07-06 Giacomo De Palma , Andrea Mari , Seth Lloyd , Vittorio Giovannetti

The quantum Cram\'er-Rao bound sets a fundamental limit on the accuracy of unbiased parameter estimation in quantum systems, relating the uncertainty in determining a parameter to the inverse of the quantum Fisher information. We…

There exist diverse no-go theorems, ranging from no-cloning to monogamies of quantum correlations and Bell inequality violations, which restrict the processing of information in the quantum world. In a multipartite scenario, monogamy of…

Quantum Physics · Physics 2015-05-26 Debasis Sadhukhan , Sudipto Singha Roy , Debraj Rakshit , Aditi Sen De , Ujjwal Sen

We present a quantum algorithm to simulate general finite dimensional Lindblad master equations without the requirement of engineering the system-environment interactions. The proposed method is able to simulate both Markovian and…

Quantum Physics · Physics 2015-06-09 R. Di Candia , J. S. Pedernales , A. del Campo , E. Solano , J. Casanova

Efficient error estimates for the Trotter product formula are central in quantum computing, mathematical physics, and numerical simulations. However, the Trotter error's dependency on the input state and its application to unbounded…

Quantum Physics · Physics 2024-11-28 Daniel Burgarth , Paolo Facchi , Alexander Hahn , Mattias Johnsson , Kazuya Yuasa

The quantum-phase-estimation algorithm (QPEA) is widely used to find estimates of unknown phases. The original algorithm relied on an input state in a uniform superposition of all possible bit strings. However, it is known that other input…

Quantum Physics · Physics 2025-05-05 Joseph G. Smith , Crispin H. W. Barnes , David R. M. Arvidsson-Shukur

The energy spectrum of Dicke Hamiltonians with and without the rotating wave approximation for arbitrary atom-number is obtained analytically with the variational method, in which the effective pseudo-spin Hamiltonian resulted from the…

Quantum Physics · Physics 2012-06-25 Jinling Lian , Yuanwei Zhang , J. -Q. Liang

Quantum Fisher information characterizes the phase sensitivity of qubits in the spin-boson model with a finite bandwidth spectrum. In contrast with Markovian reservoirs, the quantum Fisher information will flow from the environments to…

Quantum Physics · Physics 2015-06-18 Xiang Hao , Ninghua Tong , Shiqun Zhu

Despite the complexity of quantum systems in the real world, models with just a few effective many-body states often suffice to describe their quantum dynamics, provided decoherence is accounted for. We show that a machine learning…

Quantum Physics · Physics 2024-09-30 Kaustav Mukherjee , Johannes Schachenmayer , Shannon Whitlock , Sebastian Wüster