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

The generation of nonclassical states of a radiation field has become increasingly important in the past years given its various applications in quantum communication. The feasibility of generating such nonclassical states has been established in several branches of physics such as cavity electrodynamics, trapped ions, quantum dots, atoms inside cavities and so on. In this sense, we will discuss the issue of the generation of nonclassical states in the context of a superconducting qubit in a microcavity. 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. The key ingredients to engineer these quantum states are a tunable gate voltage and a classical magnetic field applied to SQUID. Some models including these ingredients and using some appropriate approximations which allow for the linearization of the interaction and nonclassical states of the field were generated. Since decoherence is known to affect quantum effects uninterruptedly and decoherence process are works even when the quantum state is being formed, therefore, it is interesting to envisage processes through which quantum superpositions are generated as fast as possible. The decoherence effect has been studied and quantified in the context of cavity QED where it is shown that the more quantum is the superposition, more rapidly the environmental effects occur during the process of creating the quantum state. In the latter reference, we have succeeded in linearizing the Hamiltonian through the application of an appropriate unitary transformation and for certain values of the parameters involved, we have showed that it is possible to obtain specific Hamiltonians. In this work we will use such approach for preparing superposition of two squeezed coherent states.Comment: arXiv admin note: substantial text overlap with arXiv:1302.5753, arXiv:1301.609

Dynamics of a superconducting qubit coupled to the quantized cavity field: a unitary transformation approach

We present a novel approach for studying the dynamics of a superconducting qubit in a cavity. We succeed in linearizing the Hamiltonian through the application of an appropriate unitary transformation followed by a rotating wave approximation (RWA). For certain values of the parameters involved, we show that it is possible to obtain a a Jaynes-Cummings type Hamiltonian. As an example, we show the existence of super-revivals for the qubit inversion

Implementation of a quantum walk in a cycle of four nodes using an alternative method based on the Swap gate

This work has the objective of implementing quantum random walks in a graph with 4 nodes represented by a circle. It was observed that during the implementation of a discrete-time quantum walk, based on Hadamard's coin, the simulated results diverge from the theoretically expected results. In order to correct the discrepancies between the processed and theoretically expected results we use an alternative method based on the Swap port. To perform the simulation of the algorithms, the Qiskit framework and a real processor provided by IBM through remote access was used. The simulations performed in the real processor showed small fluctuations, however the quantum states were obtained with satisfactory probabilities

Field Purification in the intensity-dependent Jaynes-Cummings model

We have found that, in the intensity-dependent Jaynes-Cummings model, a field initially prepared in a statistical mixture of two coherent states, $|\alpha>$ and $|-\alpha>$, evolves toward a pure state. We have also shown that an even-coherent state turns periodically a into rotated odd-coherent state during the evolution.Comment: 14 pages, RevTex, 3 figures, accepted for publication in Physics Letters

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

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.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