COLLAPSE AND REVIVAL EFFECT IN A MESOSCOPIC LC CIRCUIT

2004 ◽  
Vol 18 (08) ◽  
pp. 1217-1224 ◽  
Author(s):  
HAI-MEI LUO ◽  
YING-HUA JI ◽  
JIE LIU
Keyword(s):  
Time Evolution ◽  
Dynamic Behavior ◽  
Quantum State ◽  
Tunnel Junction ◽  
Coherent States ◽  
The State ◽  
Quantum States ◽  
Quantum Superposition ◽  
Coupling Energy ◽  
Lc Circuit

This paper studied the time evolution of quantum state in a mesoscopic LC circuit with the coupling energy caused by mesoscopic capacitor acting as a tunnel junction. It indicates that the state of the junction evolves into the quantum superposition of two coherent states and, in the state, nonclassical squeezing properties of the circuit appear. It also indicates that the dynamic behavior of the current shows collapse and revival phenomenon. The research in the paper will be helpful to miniaturize integrate circuits and electric components. It will be also important for the utilization of mesoscopic circuits to evolve the quantum states, which work as information carriers.

scholarly journals Purification and redistribution of entanglement via single local filtering

2014 ◽  
Vol 12 (01) ◽  
pp. 1450004 ◽  
Author(s):  
K. O. Yashodamma ◽  
P. J. Geetha ◽  
Sudha
Keyword(s):  
Quantum State ◽  
The State ◽  
Quantum States ◽  
Local Action ◽  
Entanglement Transfer ◽  
Local Filtering

The effect of filtering operation with respect to purification and concentration of entanglement in quantum states are discussed in this paper. It is shown, through examples, that the local action of the filtering operator on a part of the composite quantum state allows for purification of the remaining part of the state. The redistribution of entanglement in the subsystems of a noise affected state is shown to be due to the action of local filtering on the non-decohering part of the system. The varying effects of the filtering parameter, on the entanglement transfer between the subsystems, depending on the choice of the initial quantum state is illustrated.

scholarly journals Preparation of a superposition of squeezed coherent states of a cavity field via coupling to a superconducting charge qubit

2020 ◽  
Vol 16 ◽  
pp. 1
Author(s):  
Dagoberto S. Freitas
Keyword(s):  
Radiation Field ◽  
Quantum State ◽  
Coherent States ◽  
Unitary Transformation ◽  
Quantum Communication ◽  
Quantum States ◽  
Cavity Field ◽  
Nonclassical States ◽  
Charge Qubit ◽  
The Past

The generation of nonclassical states of a radiation field has become increasingly important in the past years given its various applications in quantum communication. It has been recently proposed a way to engineer quantum states using a SQUID charge qubit inside a cavity with a controllable interaction between the cavity field and the charge qubit. Since decoherence is known to affect quantum effects uninterruptedly and decoherence process are working even when the quantum state is being formed, therefore, is interesting to envisage processes through which quantum superpositions are generated as fast as possible. We succeed in linearizing the Hamiltonian of the system through the application of an appropriate unitary transformation and for certain values of the parameters involved, we show that it is possible to obtain specific Hamiltonians. In this work we will use this approach for preparing superposition of two squeezed coherent states.

SU(1,1) LIE ALGEBRA APPLIED TO THE TIME-DEPENDENT QUADRATIC HAMILTONIAN SYSTEM PERTURBED BY A SINGULARITY

2004 ◽  
Vol 18 (26) ◽  
pp. 3429-3441 ◽  
Author(s):  
JEONG RYEOL CHOI ◽  
SEONG SOO CHOI
Keyword(s):  
Hamiltonian System ◽  
Probability Density ◽  
Lie Algebra ◽  
Time Evolution ◽  
Coherent States ◽  
Classical Trajectory ◽  
Quantum States ◽  
Time Dependent ◽  
Expectation Values ◽  
Quadratic Hamiltonian

We realized SU (1,1) Lie algebra in terms of the appropriate SU (1,1) generators for the time-dependent quadratic Hamiltonian system perturbed by a singularity. Exact quantum states of the system are investigated using SU (1,1) Lie algebra. Various expectation values in two kinds of the generalized SU (1,1) coherent states, that is, BG coherent states and Perelomov coherent states are derived. We applied our study to the CKOPS (Caldirola–Kanai oscillator perturbed by a singularity). Due to the damping constant γ, the probability density of the SU (1,1) coherent states for the CKOPS converged to the center with time. The time evolution of the probability density in SU (1,1) coherent states for the CKOPS are very similar to the classical trajectory.

SUPERPOSITIONS OF COHERENT STATES AND SQUEEZING EFFECTS IN A MESOSCOPIC JOSEPHSON JUNCTION

1999 ◽  
Vol 13 (08) ◽  
pp. 917-924 ◽  
Author(s):  
JIAN ZOU ◽  
BIN SHAO
Keyword(s):  
Energy Level ◽  
Josephson Junction ◽  
Coherent States ◽  
The State ◽  
Quantum Superposition ◽  
Superconducting Ring

We consider a mesoscopic Josephson junction in a circular superconducting ring which encloses a magneto static flux. It is shown that with the junction being initially prepared in its lowest energy level the state of the junction can evolve in a quantum superposition of two coherent states, and squeezing can exist in such system.

scholarly journals Preparation of a superposition of squeezed coherent states of a cavity field via coupling to a superconducting charge qubit

2020 ◽  
Vol 16 ◽  
pp. 1-6
Author(s):  
Dagoberto S. Freitas
Keyword(s):  
Radiation Field ◽  
Quantum State ◽  
Coherent States ◽  
Unitary Transformation ◽  
Quantum Communication ◽  
Quantum States ◽  
Cavity Field ◽  
Nonclassical States ◽  
Charge Qubit ◽  
The Past

The generation of nonclassical states of a radiation field has become increasingly important in the past years given its various applications in quantum communication. It has been recently proposed a way to engineer quantum states using a SQUID charge qubit inside a cavity with a controllable interaction between the cavity field and the charge qubit. Since decoherence is known to affect quantum effects uninterruptedly and decoherence process are working even when the quantum state is being formed, therefore, is interesting to envisage processes through which quantum superpositions are generated as fast as possible. We succeed in linearizing the Hamiltonian of the system through the application of an appropriate unitary transformation and for certain values of the parameters involved, we show that it is possible to obtain specific Hamiltonians. In this work we will use this approach for preparing superposition of two squeezed coherent states.

scholarly journals Adaptive quantum state tomography with neural networks

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Yihui Quek ◽  
Stanislav Fort ◽  
Hui Khoon Ng
Keyword(s):  
Machine Learning ◽  
Quantum State ◽  
The State ◽  
Learning To Learn ◽  
Seamless Integration ◽  
Quantum State Tomography ◽  
Flexible Machine ◽  
Meta Learning ◽  
Long Time ◽  
State Tomography

AbstractCurrent algorithms for quantum state tomography (QST) are costly both on the experimental front, requiring measurement of many copies of the state, and on the classical computational front, needing a long time to analyze the gathered data. Here, we introduce neural adaptive quantum state tomography (NAQT), a fast, flexible machine-learning-based algorithm for QST that adapts measurements and provides orders of magnitude faster processing while retaining state-of-the-art reconstruction accuracy. As in other adaptive QST schemes, measurement adaptation makes use of the information gathered from previous measured copies of the state to perform a targeted sensing of the next copy, maximizing the information gathered from that next copy. Our NAQT approach allows for a rapid and seamless integration of measurement adaptation and statistical inference, using a neural-network replacement of the standard Bayes’ update, to obtain the best estimate of the state. Our algorithm, which falls into the machine learning subfield of “meta-learning” (in effect “learning to learn” about quantum states), does not require any ansatz about the form of the state to be estimated. Despite this generality, it can be retrained within hours on a single laptop for a two-qubit situation, which suggests a feasible time-cost when extended to larger systems and potential speed-ups if provided with additional structure, such as a state ansatz.

scholarly journals Gaussian quantum states can be disentangled using symplectic rotations

2021 ◽  
Vol 111 (3) ◽  
Author(s):  
Maurice A. de Gosson
Keyword(s):  
Quantum State ◽  
Covariance Matrices ◽  
Quantum States ◽  
Weyl Quantization ◽  
Symplectic Transformation ◽  
Metaplectic Operator

AbstractWe show that every Gaussian mixed quantum state can be disentangled by conjugation with a passive symplectic transformation, that is a metaplectic operator associated with a symplectic rotation. The main tools we use are the Werner–Wolf condition on covariance matrices and the symplectic covariance of Weyl quantization. Our result therefore complements a recent study by Lami, Serafini, and Adesso.

MULTIPARTY REMOTELY PREPARING MULTIPARTITE EQUATORIAL ENTANGLED STATES IN HIGH DIMENSIONS

2011 ◽  
Vol 09 (06) ◽  
pp. 1437-1448
Author(s):  
YI-BAO LI ◽  
KUI HOU ◽  
SHOU-HUA SHI
Keyword(s):  
Quantum State ◽  
Quantum Channel ◽  
Success Probability ◽  
Quantum States ◽  
Remote State Preparation ◽  
Entangled States ◽  
Entangled State ◽  
High Dimensions ◽  
Original State ◽  
State Preparation

We propose two kinds of schemes for multiparty remote state preparation (MRSP) of the multiparticle d-dimensional equatorial quantum states by using partial entangled state as the quantum channel. Unlike more remote state preparation scheme which only one sender knows the original state to be remotely prepared, the quantum state is shared by two-party or multiparty in this scheme. We show that if and only if all the senders agree to collaborate with each other, the receiver can recover the original state with certain probability. It is found that the total success probability of MRSP is only by means of the smaller coefficients of the quantum channel and the dimension d.

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