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 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.

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.

Four-directional quantum controlled teleportation using a single quantum resource

2020 ◽  
Vol 34 (35) ◽  
pp. 2050412
Author(s):  
Xin-Wei Zha ◽  
Ke Li
Keyword(s):  
Information Transmission ◽  
Quantum State ◽  
Quantum Teleportation ◽  
Unitary Transformation ◽  
Quantum States ◽  
Controlled Teleportation ◽  
Single Quantum ◽  
State Information ◽  
Information State ◽  
Entanglement Property

In this paper, a quantum teleportation protocol has been proposed that can simultaneously transmit quantum states in four directions using a single entangled channel. This means that there are four senders who want to transmit state information, and they are Alice, Bob, Charlie, and David. In order to ensure the security of information transmission, the information state of the four is transmitted to four receivers Fancy1, Fancy2, Fancy3, and Fancy4 under the control of the controller Elle. Through unitary transformation and entanglement property, receivers can recover the original quantum state from the four senders, which is easy to implement. The teleportation protocol is perfect.

scholarly journals Quantum communication with coherent states of light

2017 ◽  
Vol 375 (2099) ◽  
pp. 20160235 ◽  
Author(s):  
Imran Khan ◽  
Dominique Elser ◽  
Thomas Dirmeier ◽  
Christoph Marquardt ◽  
Gerd Leuchs
Keyword(s):  
Coherent States ◽  
Secure Communication ◽  
Communication Systems ◽  
Quantum Communication ◽  
Continuous Variable ◽  
Quantum States ◽  
Complexity Of Algorithms ◽  
Laser Systems ◽  
Quantum Technology ◽  
Photon States

Quantum communication offers long-term security especially, but not only, relevant to government and industrial users. It is worth noting that, for the first time in the history of cryptographic encoding, we are currently in the situation that secure communication can be based on the fundamental laws of physics (information theoretical security) rather than on algorithmic security relying on the complexity of algorithms, which is periodically endangered as standard computer technology advances. On a fundamental level, the security of quantum key distribution (QKD) relies on the non-orthogonality of the quantum states used. So even coherent states are well suited for this task, the quantum states that largely describe the light generated by laser systems. Depending on whether one uses detectors resolving single or multiple photon states or detectors measuring the field quadratures, one speaks of, respectively, a discrete- or a continuous-variable description. Continuous-variable QKD with coherent states uses a technology that is very similar to the one employed in classical coherent communication systems, the backbone of today’s Internet connections. Here, we review recent developments in this field in two connected regimes: (i) improving QKD equipment by implementing front-end telecom devices and (ii) research into satellite QKD for bridging long distances by building upon existing optical satellite links. This article is part of the themed issue ‘Quantum technology for the 21st century’.

scholarly journals Quantum-state transfer between atom and macroscopically distinguishable cavity field in Jaynes–Cummings model

2015 ◽  
Vol 13 (01) ◽  
pp. 1550001
Author(s):  
Gang Zhang ◽  
Guan-Rong Li ◽  
Zhi Song
Keyword(s):  
Quantum State ◽  
Coherent States ◽  
Spin Echo ◽  
Cavity Field ◽  
Quantum State Transfer ◽  
Alternative Scheme ◽  
State Transfer ◽  
Pauli Matrix ◽  
Cavity System ◽  
Non Local

We present a scheme for transferring quantum state between atom and cavity field in Jaynes–Cummings model (JC) in the aid of spin-echo-like technique. It is based on the facts that the atom in a cavity can induce the generation of modified coherent states (MCSs), which can be shown to be macroscopically distinguishable, and the anti-commutation relation between the Hamiltonian and the z-component Pauli matrix. We show that this scheme is applicable for a class of cavity field states. The application on two-cavity system provides an alternative scheme for preparation of non-local superpositions of quasi-classical light states. Numerical simulation shows that the proposed schemes are efficient.

scholarly journals QUANTUM DISCORD AS A RESOURCE IN QUANTUM COMMUNICATION

2012 ◽  
Vol 27 (01n03) ◽  
pp. 1345041 ◽  
Author(s):  
VAIBHAV MADHOK ◽  
ANIMESH DATTA
Keyword(s):  
Quantum State ◽  
Quantum Coherence ◽  
Quantum Discord ◽  
Quantum Communication ◽  
Quantum States ◽  
Quantitative Relation ◽  
Dense Coding ◽  
Open Questions ◽  
Communication Processes ◽  
Quantum Protocols

As quantum technologies move from the issues of principle to those of practice, it is important to understand the limitations on attaining tangible quantum advantages. In the realm of quantum communication, quantum discord captures the damaging effects of a decoherent environment. This is a consequence of quantum discord quantifying the advantage of quantum coherence in quantum communication. This establishes quantum discord as a resource for quantum communication processes. We discuss this progress, which derives a quantitative relation between the yield of the fully quantum Slepian–Wolf (FQSW) protocol in the presence of noise and the quantum discord of the state involved. The significance of quantum discord in noisy versions of teleportation, super-dense coding, entanglement distillation and quantum state merging are discussed. These results lead to open questions regarding the tradeoff between quantum entanglement and discord in choosing the optimal quantum states for attaining palpable quantum advantages in noisy quantum protocols.

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.

scholarly journals Path-encoded high-dimensional quantum communication over a 2-km multicore fiber

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Beatrice Da Lio ◽  
Daniele Cozzolino ◽  
Nicola Biagi ◽  
Yunhong Ding ◽  
Karsten Rottwitt ◽  
...  
Keyword(s):  
Quantum Key Distribution ◽  
Quantum Communication ◽  
Error Rates ◽  
Quantum States ◽  
High Dimensional ◽  
Secret Key ◽  
System A ◽  
Reliable Transmission ◽  
Multicore Fiber ◽  
Interferometric Detection

AbstractQuantum key distribution (QKD) protocols based on high-dimensional quantum states have shown the route to increase the key rate generation while benefiting of enhanced error tolerance, thus overcoming the limitations of two-dimensional QKD protocols. Nonetheless, the reliable transmission through fiber links of high-dimensional quantum states remains an open challenge that must be addressed to boost their application. Here, we demonstrate the reliable transmission over a 2-km-long multicore fiber of path-encoded high-dimensional quantum states. Leveraging on a phase-locked loop system, a stable interferometric detection is guaranteed, allowing for low error rates and the generation of 6.3 Mbit/s of a secret key rate.

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.

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