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A classical thermometer typically works by exchanging energy with the system being measured until it comes to equilibrium, at which point the readout is related to the final energy state of the thermometer. A recent paper noted that…

Quantum Physics · Physics 2016-09-07 W. K. Tham , H. Ferretti , A. V. Sadashivan , A. M. Steinberg

Measuring the temperature of a quantum system is an essential task in almost all aspects of quantum technologies. Theoretically, an optimal strategy for thermometry requires measuring energy which demands full accessibility over the entire…

Quantum Physics · Physics 2024-03-18 Yaoling Yang , Victor Montenegro , Abolfazl Bayat

Measurement-based quantum computation utilizes an initial entangled resource state and proceeds with subsequent single-qubit measurements. It is implicitly assumed that the interactions between qubits can be switched off so that the…

Quantum Physics · Physics 2011-08-08 Ying Li , Daniel E. Browne , Leong Chuan Kwek , Robert Raussendorf , Tzu-Chieh Wei

We propose a solid-state experiment to study the process of continuous quantum measurement of a qubit state. The experiment would verify that an individual qubit stays coherent during the process of measurement (in contrast to the gradual…

Mesoscale and Nanoscale Physics · Physics 2009-10-31 Alexander N. Korotkov

The calculation of excited state energies of electronic structure Hamiltonians has many important applications, such as the calculation of optical spectra and reaction rates. While low-depth quantum algorithms, such as the variational…

Quantum Physics · Physics 2019-07-03 Oscar Higgott , Daochen Wang , Stephen Brierley

We propose a quantum charging scheme fueled by measurements on ancillary qubits serving as disposable chargers. A stream of identical qubits are sequentially coupled to a quantum battery of $N+1$ levels and measured by projective operations…

Quantum Physics · Physics 2023-07-04 Jia-shun Yan , Jun Jing

The simulation of molecular electronic structure is an important application of quantum devices. Recently, it has been shown that quantum devices can be effectively combined with classical supercomputing centers in the context of the…

Quantum Physics · Physics 2025-02-28 Stefano Barison , Javier Robledo Moreno , Mario Motta

Excited states of molecules lie in the heart of photochemistry and chemical reactions. The recent development in quantum computational chemistry leads to inventions of a variety of algorithms that calculate the excited states of molecules…

Quantum Physics · Physics 2020-11-05 Hiroki Kawai , Yuya O. Nakagawa

We study, from a thermodynamic perspective, the equilibrium states of a qubit interacting with an arbitrary environment of dimension N>>2. We show that even in presence of memory about the initial state, in some cases the qubit can be…

Quantum Physics · Physics 2018-10-31 Andrés Vallejo , Alejandro Romanelli , Raul Donangelo

A measurement-based quantum computer could consist of a local-gapped Hamiltonian system, whose thermal states --at sufficiently low temperature-- are universal resources for the computation. Initialization of the computer would correspond…

Quantum Physics · Physics 2015-06-18 G. H. Aguilar , T. Kolb , D. Cavalcanti , L. Aolita , R. Chaves , S. P. Walborn , P. H. Souto Ribeiro

We design a measurement-based quantum refrigerator with an arbitrary number of qubits situated in a one-dimensional array that interact through variable-range XY interactions. The method proposed is based on repeated evolution followed by a…

Quantum Physics · Physics 2022-09-19 Tanoy Kanti Konar , Srijon Ghosh , Aditi Sen De

Distinguishing hot from cold is the most primitive form of thermometry. Here we consider how well this task can be performed using a single qubit to distinguish between two different temperatures of a bosonic bath. In this simple setting,…

Quantum Physics · Physics 2015-02-04 Sania Jevtic , David Newman , Terry Rudolph , T. M. Stace

A key hurdle to the success of quantum computers is the ability to initialize qubits into a pure state, which can be achieved by cooling qubits down to very low temperatures. Computational cooling of qubits, whereby a subset of the qubits…

Quantum Physics · Physics 2024-10-18 Giuliano Difranco , Lindsay Bassman Oftelie

Many quantum technologies, including quantum computers, quantum heat engines, and quantum sensors, rely on operating conditions in the subkelvin regime. It is therefore desirable to develop practical tools and methods for the precise…

Mesoscale and Nanoscale Physics · Physics 2025-03-28 Riya Baruah , Pedro Portugal , Joachim Wabnig , Christian Flindt

We investigate the measurements of two-state quantum systems (qubits) at finite temperatures using a resonant harmonic oscillator as a quantum probe. The reduced density matrix and oscillator correlators are calculated by a scheme combining…

Mesoscale and Nanoscale Physics · Physics 2009-11-11 Teemu Ojanen , Tero T. Heikkila

Each cycle of a quantum computation requires a quantum state initialisation. For semiconductor-based quantum platforms, initialisation is typically performed via slow microwave processes and usually requires cooling to temperatures where…

Quantum annealing has been demonstrated with superconducting qubits. Such a quantum annealer has been used to solve combinatorial optimization problems. Moreover, it serves as a quantum simulator for investigating the properties of quantum…

Quantum Physics · Physics 2025-07-16 Takashi Imoto , Yuki Susa , Ryoji Miyazaki , Yuichiro Matsuzaki

Graph states are entangled resource states for universal measurement-based quantum computation. Although matter qubits such as superconducting circuits and trapped ions are promising candidates to generate graph states, it is…

Quantum Physics · Physics 2022-07-07 Kazuki Akimoto , Shunji Tsuchiya , Ryosuke Yoshii , Yuki Takeuchi

The unknown temperature of a sample may be estimated with minimal disturbance by putting it in thermal contact with an individual quantum probe. If the interaction time is sufficiently long so that the probe thermalizes, the temperature can…

Quantum Physics · Physics 2015-06-09 Luis A. Correa , Mohammad Mehboudi , Gerardo Adesso , Anna Sanpera

We solve the master equations of two charged qubits measured by two serially coupled quantum point contacts (QPCs). We describe two-qubit dynamics by comparing entangled states with product states, and show that the QPC current can be used…

Mesoscale and Nanoscale Physics · Physics 2015-06-24 Tetsufumi Tanamoto , Xuedong Hu