scholarly journals Time-dependent Pancharatnam phases and quantum correlations for coupling superconducting two-qubit system with dissipative environment

2020 ◽  
Vol 50 (4) ◽  
Author(s):  
Liyuan Xue ◽  
Z.S. Wang
Keyword(s):  
Quantum Computation ◽  
Quantum Correlations ◽  
Superconducting Qubits ◽  
Time Dependent ◽  
Mixed States ◽  
Pancharatnam Phase ◽  
Qubit System ◽  
Phonon Number ◽  
Dissipative Environment

Two coupling superconducting qubits are studied for the quantum concurrence, discord, and Pancharatnam phase, for the X and Y states under the dephasing and instantaneous decay environment as well as their couplings. We find that the X and Y states are special mixed states according to the Bloch radius. In general, the larger the environment and phonon number are at the larger region of time, the larger the quantum concurrence and discord are. But we find that the environment correlations are helpful to implement the quantum computation. The Pancharatnam phases provide a way to distinguish the X and Y states.

Geometric phase of two-qubit system in dephasing environment

2015 ◽  
Vol 29 (32) ◽  
pp. 1550236 ◽  
Author(s):  
Xiaoya Cai ◽  
Hui Pan ◽  
Z. S. Wang
Keyword(s):  
Phase Change ◽  
Quantum Computation ◽  
Geometric Phase ◽  
Berry Phase ◽  
Initial Conditions ◽  
The Other ◽  
Time Dependent ◽  
Pancharatnam Phase ◽  
Coupling System ◽  
Qubit System

We investigated the geometric phase for interaction between superconducting two-qubit system in dephased environment. The Pancharatnam phase and the Berry phase are studied. Numerical results are discussed. By considering the differently initial conditions, we find that the time-dependent Pancharatnam phase keeps the initial entangling message. On the other hand, the transition of Pancharatnam phase is dependent of the phase change in the superconducting two-qubit coupling system. Our results may be helpful to implement the time-dependent geometric quantum computation.

scholarly journals A study of quantum correlations in open quantum systems

2011 ◽  
Vol 11 (7&8) ◽  
pp. 541-562
Author(s):  
Indranil Chakrabarty ◽  
Subhashish Banerjee ◽  
Nana Siddharth
Keyword(s):  
Open Quantum Systems ◽  
Quantum Correlations ◽  
Quantum Systems ◽  
Bell’S Inequality ◽  
Mixed States ◽  
Classical Correlation ◽  
Bell's Inequality ◽  
Qubit System ◽  
Dynamical Parameters ◽  
Potential Resource

In this work, we study quantum correlations in mixed states. The states studied are modeled by a two-qubit system interacting with its environment via a quantum non demolition (purely dephasing) as well as dissipative type of interaction. The entanglement dynamics of this two qubit system is analyzed. We make a comparative study of various measures of quantum correlations, like Concurrence, Bell's inequality, Discord and Teleportation fidelity, on these states, generated by the above evolutions. We classify these evoluted states on basis of various dynamical parameters like bath squeezing parameter $r$, inter-qubit spacing $r_{12}$, temperature $T$ and time of system-bath evolution $t$. In this study, in addition we report the existence of entangled states which do not violate Bell's inequality, but can still be useful as a potential resource for teleportation. Moreover we study the dynamics of quantum as well as classical correlation in presence of dissipative coherence.

Strongly correlated quantum walks with a 12-qubit superconducting processor

Science ◽  
2019 ◽  
Vol 364 (6442) ◽  
pp. 753-756 ◽  
Author(s):  
Zhiguang Yan ◽  
Yu-Ran Zhang ◽  
Ming Gong ◽  
Yulin Wu ◽  
Yarui Zheng ◽  
...  
Keyword(s):  
Quantum Computation ◽  
Large Scale ◽  
Quantum Walks ◽  
Superconducting Qubits ◽  
Time Dependent ◽  
Strongly Correlated ◽  
Superconducting Qubit ◽  
Many Body ◽  
Universal Quantum ◽  
Many Body Systems

Quantum walks are the quantum analogs of classical random walks, which allow for the simulation of large-scale quantum many-body systems and the realization of universal quantum computation without time-dependent control. We experimentally demonstrate quantum walks of one and two strongly correlated microwave photons in a one-dimensional array of 12 superconducting qubits with short-range interactions. First, in one-photon quantum walks, we observed the propagation of the density and correlation of the quasiparticle excitation of the superconducting qubit and quantum entanglement between qubit pairs. Second, when implementing two-photon quantum walks by exciting two superconducting qubits, we observed the fermionization of strongly interacting photons from the measured time-dependent long-range anticorrelations, representing the antibunching of photons with attractive interactions. The demonstration of quantum walks on a quantum processor, using superconducting qubits as artificial atoms and tomographic readout, paves the way to quantum simulation of many-body phenomena and universal quantum computation.

scholarly journals Realization of High-Fidelity Controlled-Phase Gates in Extensible Superconducting Qubits Design with a Tunable Coupler

2021 ◽  
Vol 38 (10) ◽  
pp. 100301
Author(s):  
Yangsen Ye ◽  
Sirui Cao ◽  
Yulin Wu ◽  
Xiawei Chen ◽  
Qingling Zhu ◽  
...  
Keyword(s):  
Quantum Computation ◽  
Large Scale ◽  
Quantum Systems ◽  
Superconducting Qubits ◽  
Cross Entropy ◽  
High Fidelity ◽  
Average Fidelity ◽  
Control Error ◽  
Qubit System ◽  
Parasitic Coupling

High-fidelity two-qubit gates are essential for the realization of large-scale quantum computation and simulation. Tunable coupler design is used to reduce the problem of parasitic coupling and frequency crowding in many-qubit systems and thus thought to be advantageous. Here we design an extensible 5-qubit system in which center transmon qubit can couple to every four near-neighboring qubits via a capacitive tunable coupler and experimentally demonstrate high-fidelity controlled-phase (CZ) gate by manipulating central qubit and one near-neighboring qubit. Speckle purity benchmarking and cross entropy benchmarking are used to assess the purity fidelity and the fidelity of the CZ gate. The average purity fidelity of the CZ gate is 99.69±0.04% and the average fidelity of the CZ gate is 99.65±0.04%, which means that the control error is about 0.04%. Our work is helpful for resolving many challenges in implementation of large-scale quantum systems.

scholarly journals Flux-based superconducting qubits for quantum computation

2002 ◽  
Vol 372-376 ◽  
pp. 194-200 ◽  
Author(s):  
T.P. Orlando ◽  
S. Lloyd ◽  
L.S. Levitov ◽  
K.K. Berggren ◽  
M.J. Feldman ◽  
...  
Keyword(s):  
Quantum Computation ◽  
Superconducting Qubits

Thermal quantum correlations in the two-qubit Heisenberg XYZ spin chain with Dzyaloshinskii–Moriya interaction

2021 ◽  
pp. 2150074
Author(s):  
Youssef Khedif ◽  
Mohammed Daoud
Keyword(s):  
Quantum Correlations ◽  
Thermal Fluctuations ◽  
Quantum Nonlocality ◽  
Chain Model ◽  
Trace Distance ◽  
Heisenberg Spin ◽  
Logarithmic Negativity ◽  
Qubit System ◽  
Classical Correlations ◽  
Moriya Interaction

We investigate the quantum correlations of a two-qubit XYZ Heisenberg spin-1/2 chain model with Dzyaloshinskii–Moriya interaction. The two-qubit system is considered in thermal equilibrium. The variations of logarithmic negativity, uncertainty-induced quantum nonlocality (UIN) and trace distance discord, versus the parameters characterizing the system, are analyzed. The results show that the UIN measure captures quantum correlations that cannot be revealed by entanglement and trace discord. We also show that the Dzyaloshinskii–Moriya interaction enhances the non-classical correlations between the spins and can weaken the undesirable destructive effects of thermal fluctuations. In addition, an entangled–unentangled phase transition can be detected from the behavior of logarithmic negativity.

Phase control for entanglement preparation in two-qubit systems

2005 ◽  
Vol 5 (4&5) ◽  
pp. 364-379
Author(s):  
V.S. Malinovsky ◽  
I.R. Sola
Keyword(s):  
Quantum Information ◽  
Quantum Computation ◽  
Quantum Control ◽  
Phase Control ◽  
Adiabatic Passage ◽  
Pulse Parameters ◽  
Qubit System ◽  
Phase Manipulation ◽  
Laser Control ◽  
Pi Pulses

The theory of Quantum Control is starting to lay bridges with the field of Quantum Information and Quantum Computation. Using key ideas of laser control of the dynamics by means of phase manipulation and adiabatic passage, we review laser schemes that allow entanglement preparation in a two-qubit system. The schemes are based on sequences that use four time-delayed pulses, with or without concerted decay, in or off resonance with the intermediate levels of the qubit space. We show how to control the fidelity and phase of the entanglement, as well as the sensitivity of the preparation to the different pulse parameters. In general the schemes provide an improvement in robustness and in the finesse of the control to phase, with respect to previously proposed schemes based on sequences of $\pi$ pulses.

scholarly journals Bounds on Mixed State Entanglement

Entropy ◽  
2020 ◽  
Vol 22 (1) ◽  
pp. 62 ◽  
Author(s):  
Bruno Leggio ◽  
Anna Napoli ◽  
Hiromichi Nakazato ◽  
Antonino Messina
Keyword(s):  
Mixed State ◽  
General Framework ◽  
Quantum Correlations ◽  
Thermal Entanglement ◽  
Mixed States ◽  
Clear Explanation ◽  
Finite Dimensionality ◽  
Partial Transpose ◽  
The Subject

In the general framework of d 1 × d 2 mixed states, we derive an explicit bound for bipartite negative partial transpose (NPT) entanglement based on the mixedness characterization of the physical system. The derived result is very general, being based only on the assumption of finite dimensionality. In addition, it turns out to be of experimental interest since some purity-measuring protocols are known. Exploiting the bound in the particular case of thermal entanglement, a way to connect thermodynamic features to the monogamy of quantum correlations is suggested, and some recent results on the subject are given a physically clear explanation.

Sign in / Sign up

Export Citation Format

Share Document