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Preparing thermal states on a quantum computer can have a variety of applications, from simulating many-body quantum systems to training machine learning models. Variational circuits have been proposed for this task on near-term quantum…

Quantum Physics · Physics 2021-11-09 Jonathan Foldager , Arthur Pesah , Lars Kai Hansen

In measurement-based quantum computing an algorithm is performed by measurements on highly-entangled resource states. To date, several implementations were demonstrated, all of them assuming perfect noise-free environments. Here we consider…

Studies about Quantum Information Theory continue actively in many research institutions. Very recently, pratical setups of large scale quantum computers are widely studied e.g. quantum repeaters, memories and processors. Entanglement…

Quantum Physics · Physics 2017-05-16 Volkan Erol

With an ever-expanding ecosystem of noisy and intermediate-scale quantum devices, exploring their possible applications is a rapidly growing field of quantum information science. In this work, we demonstrate that variational quantum…

Quantum Physics · Physics 2021-07-16 Johannes Jakob Meyer , Johannes Borregaard , Jens Eisert

We propose a quantum-classical hybrid algorithm to encode a given arbitrarily quantum state $\vert \Psi \rangle$ onto an optimal quantum circuit $\hat{\mathcal{C}}$ with a finite number of single- and two-qubit quantum gates. The proposed…

Quantum Physics · Physics 2024-10-16 Tomonori Shirakawa , Hiroshi Ueda , Seiji Yunoki

Several applications of quantum machine learning (QML) rely on a quantum measurement followed by training algorithms using the measurement outcomes. However, recently developed QML models, such as variational quantum circuits (VQCs), can be…

Quantum Physics · Physics 2023-08-31 Hossein T. Dinani , Diego Tancara , Felipe F. Fanchini , Ariel Norambuena , Raul Coto

Studies of quantum metrology have shown that the use of many-body entangled states can lead to an enhancement in sensitivity when compared to product states. In this paper, we quantify the metrological advantage of entanglement in a setting…

Quantum state preparation is an important subroutine for quantum computing. We show that any $n$-qubit quantum state can be prepared with a $\Theta(n)$-depth circuit using only single- and two-qubit gates, although with a cost of an…

Quantum Physics · Physics 2023-04-25 Xiao-Ming Zhang , Tongyang Li , Xiao Yuan

Quantum metrology enables sensitivity to approach the limits set by fundamental physical laws. Even a single continuous mode offers enhanced precision, with the improvement scaling with its occupation number. Due to their high information…

Quantum Physics · Physics 2025-12-10 Piotr T. Grochowski , Radim Filip

Efficient encoding of classical information plays a fundamental role in numerous practical quantum algorithms. However, the preparation of an arbitrary amplitude-encoded state has been proven to be time-consuming, and its deployment on…

Quantum Physics · Physics 2025-08-19 Chao Wang , Pengrui Zhou , Xi-Ning Zhuang , Ziwei Cui , Menghan Dou , Zhao-Yun Chen , Guo-Ping Guo

Measurements in quantum mechanics cannot perfectly distinguish all states and necessarily disturb the measured system. We present and analyse a proposal to demonstrate fundamental limits on quantum control of a single qubit arising from…

The efficiency of a quantum metrology protocol can be significantly diminished by the interaction of the system with its environment, leading to a loss of purity and, as a result, a mixed state for the probing system. An example is the…

Quantum Physics · Physics 2025-02-28 Eduardo Serrano-Ensástiga , Chryssomalis Chryssomalakos , John Martin

Quantum computing is among the most promising emerging techniques to solve problems that are computationally intractable on classical hardware. A large body of existing works focus on using variational quantum algorithms on the gate level…

The preparation of long-range entangled states using unitary circuits is limited by Lieb-Robinson bounds, but circuits with projective measurements and feedback (``adaptive circuits'') can evade such restrictions. We introduce three classes…

Strongly Correlated Electrons · Physics 2023-04-14 Tsung-Cheng Lu , Leonardo A. Lessa , Isaac H. Kim , Timothy H. Hsieh

We investigate a probe state preparation protocol based on two non-selective generalized quantum measurements to enhance parameter estimation in single-qubit systems. By fine-tuning the measurement strengths, we demonstrate the ability to…

Quantum Physics · Physics 2026-05-13 Jonas F. G. Santos , Shanhe Su , Moises Rojas

We unify Ramsey, twist-untwist, and random quantum sensors using operator algebra and account for the Fisher scaling of various sensor designs. We illustrate how the operator orbits associated with state preparation inform the scaling of…

Quantum Physics · Physics 2025-12-16 Sooryansh Asthana , Yeshma Ibrahim , Norman Tze Wei Koo , Sai Vinjanampathy

Preparation of quantum states is of vital importance for performing quantum computations and quantum simulations. In this work, we propose a general framework for preparing ground states of many-body systems by combining the…

Quantum Gases · Physics 2023-08-10 Yadong Wu , Juan Yao , Pengfei Zhang

As one of the most prominent subfields of quantum communication research, remote state preparation (RSP) plays a crucial role in quantum networks. Here we present a deterministic remote state preparation scheme to prepare an arbitrary…

Quantum Physics · Physics 2023-02-21 Deepak Singh , Sanjeev Kumar , Bikash K. Behera

This study explores robust entangled states described using the framework of discrete Wigner functions. Notably, these states are known to outperform the Bell state in measures of entanglement in the presence of non-Markovian noise. Our…

Quantum Physics · Physics 2025-05-01 Jai Lalita , Pavithran Iyer , Subhashish Banerjee

Quantum metrology explores optimal quantum protocols for parameter estimation. In the context of optical atomic clocks, conventional protocols focus on optimal input states and measurements to achieve enhanced sensitivities. However, such…

Quantum Physics · Physics 2025-09-03 Su Direkci , Manuel Endres , Tuvia Gefen