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We study the modification of the second law of thermodynamics for a quantum system interacting with a reservoir regarding quantum coherence. The whole system is isolated so that neither energy nor information is lost. It is discovered that…

Quantum Physics · Physics 2021-10-12 Yu-Han Ma , C. L. Liu , C. P. Sun

We apply the quantum optimal control theory based on the Krotov method to implement single-qubit $X$ and $Z$ gates and two-qubit CNOT gates for inductively coupled superconducting flux qubits with fixed qubit transition frequencies and…

Quantum Physics · Physics 2014-07-16 Shang-Yu Huang , Hsi-Sheng Goan

A heat engine operating in the one-shot finite-size regime, where systems composed of a small number of quantum particles interact with hot and cold baths and are restricted to one-shot measurements, delivers fluctuating work. Further,…

Quantum Physics · Physics 2021-02-15 Mohit Lal Bera , Maciej Lewenstein , Manabendra Nath Bera

Quantum optimal control theory allows to design accurate quantum gates. We employ it to design high-fidelity two-bit gates for Josephson charge qubits in the presence of both leakage and noise. Our protocol considerably increases the…

Quantum Physics · Physics 2009-11-13 Simone Montangero , Tommaso Calarco , Rosario Fazio

Quantum heat engines form an active field of research due to their potential applications. There are several phenomena that are unique to the quantum regime, some of which are known to give these engines an edge over their classical…

Statistical Mechanics · Physics 2023-06-14 Ashutosh Kumar , Trilochan Bagarti , Sourabh Lahiri , Subhashish Banerjee

As the field of quantum computing grows, novel algorithms which take advantage of quantum phenomena need to be developed. As we are currently in the NISQ (noisy intermediate scale quantum) era, quantum algorithm researchers cannot reliably…

Quantum Physics · Physics 2024-11-28 Youssef Moawad , Andrew Brown , René Steijl , Wim Vanderbauwhede

The introduction of the quantum analogue of a Carnot engine based on a bath comprising of particles with a small amount of coherence initiated an active line of research on the harnessing of different quantum resources for the enhancement…

Quantum Physics · Physics 2022-12-23 Kenza Hammam , Heather Leitch , Yassine Hassouni , Gabriele De Chiara

We demonstrate that conditional as well as unconditional basic operations which are prerequisite for universal quantum gates can be performed with almost 100% fidelity within a strongly interacting two-electron quantum ring. Both sets of…

Mesoscale and Nanoscale Physics · Physics 2016-08-14 Lene Sælen , Erik Waltersson , J. P. Hansen , Eva Lindroth

Increasing quantum circuit fidelity requires an efficient instruction set to avoid errors from decoherence. The choice of a two-qubit (2Q) hardware basis gate depends on a quantum modulator's native Hamiltonian interactions and applied…

Quantum Physics · Physics 2025-04-22 Evan McKinney , Chao Zhou , Mingkang Xia , Michael Hatridge , Alex K. Jones

Optical qubits uniquely combine information transfer in optical fibers with a good processing capability and are therefore attractive tools for quantum technologies. A large challenge, however, is to overcome the low efficiency of two-qubit…

Successful implementation of a fault-tolerant quantum computation on a system of qubits places severe demands on the hardware used to control the many-qubit state. It is known that an accuracy threshold $P_{a}$ exists for any quantum gate…

Quantum Physics · Physics 2014-08-18 Yuchen Peng , Frank Gaitan

We examine the effectiveness and resilience of achieving quantum gates employing three approaches stemming from quantum control methods: counterdiabatic driving, Floquet engineering, and inverse engineering. We critically analyse their…

Quantum Physics · Physics 2023-08-30 Eoin Carolan , Barış Çakmak , Steve Campbell

We review quantum information processing with cold neutral particles, that is, atoms or polar molecules. First, we analyze the best suited degrees of freedom of these particles for storing quantum information, and then we discuss both…

Quantum Physics · Physics 2011-11-01 Antonio Negretti , Philipp Treutlein , Tommaso Calarco

We demonstrate complete characterization of a two-qubit entangling process - a linear optics controlled-NOT gate operating with coincident detection - by quantum process tomography. We use maximum-likelihood estimation to convert the…

Quantum Physics · Physics 2008-11-26 J. L. O'Brien , G. J. Pryde , A. Gilchrist , D. F. V. James , N. K. Langford , T. C. Ralph , A. G. White

Full connectivity of qubits is necessary for most quantum algorithms, which is difficult to directly implement on Noisy Intermediate-Scale Quantum processors. However, inserting swap gate to enable the two-qubit gates between uncoupled…

Quantum Physics · Physics 2021-02-03 Bin-Han Lu , Yu-Chun Wu , Wei-Cheng Kong , Qi Zhou , Guo-Ping Guo

There is a recent surge of interest and insights regarding the interplay of quantum optimal control and variational quantum algorithms. We study the framework in the context of qudits which are, for instance, definable as controllable…

Quantum Physics · Physics 2022-10-26 A. Barış Özgüler , Davide Venturelli

A quantum computer based on an asymmetric coupled dot system has been proposed and shown to operate as the controlled-NOT-gate. The basic idea is (1) the electron is localized in one of the asymmetric coupled dots. (2)The electron transfer…

Quantum Physics · Physics 2008-12-18 Tetsufumi Tanamoto

Spin qubits in quantum dots define an attractive platform for scalable quantum information because of their compatibility with semiconductor manufacturing, their long coherence times, and the ability to operate at temperatures exceeding one…

Mesoscale and Nanoscale Physics · Physics 2020-07-20 L. Petit , M. Russ , H. G. J. Eenink , W. I. L. Lawrie , J. S. Clarke , L. M. K. Vandersypen , M. Veldhorst

Optimal implementation of quantum gates is crucial for designing a quantum computer. We consider the matrix representation of an arbitrary multiqubit gate. By ordering the basis vectors using the Gray code, we construct the quantum circuit…

Quantum Physics · Physics 2007-05-23 Juha J. Vartiainen , Mikko Mottonen , Martti M. Salomaa

We demonstrate the use of optimal control to design two entropy-manipulating quantum gates which are more complex than the corresponding, commonly used, gates, such as CNOT and Toffoli (CCNOT): A 2-qubit gate called PE (polarization…

Quantum Physics · Physics 2014-11-19 Yosi Atia , Yuval Elias , Tal Mor , Yossi Weinstein