Zhan Zhi-Ming

Remote Preparation of an Entangled State in Nonideal Conditions

In this paper, the theoretical investigation of remote preparation of an entangled state is studied in nonideal conditions. Our studies include two parts. In the first part, we consider the remote state preparation (RSP) of an entangled state through two equally noisy quantum channel states, namely, a mixture of Bell states. Studies show there is a particular mixed-state channel for which all pure entangled states remain entangled after this inexact RSP. In the second part, we suppose that noises which quantum channels suffer from can be expressed as the Lindblad operators. The master equation of the system can be expressed in the Lindblad form. Through solving the master equation, we calculate the fidelity as a function of decoherence rates and parameters of the state to be prepared. For a given entangled state, we investigate the influence of different types of noises on the fidelity.

Voltage-controlled entanglement and quantum-information transfer between spatially separated quantum-dot molecules

We propose two schemes for generating entanglement and quantum-state transfer (QST) between two spatially separated semiconductor quantum dot molecules (QDMs) based on voltage-controlled tunneling effects. In the present schemes, two QDMs are trapped in two spatially separated cavities connected by a fiber. By numerically simulating the evolution of the system, we show that the generation of entanglement and QST can be controlled by an external gate voltage in our schemes. Moreover, proposed schemes are robust against the noise of system parameters.

Possible Realization of Cluster States and Quantum Information Transfer in Cavity QED via Raman Transition

We present a scheme to generate cluster states with many atoms in cavity QED via Raman transition. In this scheme, no transfer of quantum information between the atoms and cavities is required, the cavity fields are only virtually excited and thus the cavity decay is suppressed during the generation of cluster states. The atoms are always populated in the two ground states. Therefore, the scheme is insensitive to the atomic spontaneous emission and cavity decay. We also show how to transfer quantum information from one atom to another.

Efficient Scheme for Greenberger–Horne–Zeilinger State and Cluster State with Trapped Ions

We propose a scheme to generate the Greenberger?Horne?Zeilinger (GHZ) states and the cluster states of many trapped ions. In the scheme, the ion is illuminated by a single laser tuned to the first lower vibrational sideband. The scheme only requires resonant interactions. Thus the scheme is very simple and the quantum dynamics operation can be realized at a high speed, which is important in view of decoherence.

Shaping of few-cycle laser pulses via a subwavelength structure

We theoretically investigate the propagation of few-cycle laser pulses in resonant two-level dense media with a subwavelength structure, which is described by the full Maxwell‐Bloch equations without the frame of slowly varying envelope and rotating wave approximations. The input pulses can be shaped into shorter ones with a single or less than one optical cycle. The effect of the parameters of the subwavelength structure and laser pulses is studied. Our study shows that the media with a subwavelength structure can significantly shape the few-cycle pulses into a subcycle pulse, even for the case of chirp pulses as input fields. This suggests that such subwavelength structures have potential application in the shaping of few-cycle laser pulses.

Preparation of Cluster States for Many Atoms in Cavity QED

We propose a scheme for the generation of the cluster states for many atoms in cavity QED. In our scheme, the atoms are sent through nonresonant cavity fields in the vacuum states. The cavity fields are only virtually excited and no quantum information will be transferred from the atoms to the cavity fields. The advantage is that the cavities are suppressed during the procedure. The scheme can also be generalized to the ion trap system.

Generation of W States with Many Superconducting-Quantum-Interference-Devices in Cavity QED

We propose a scheme to generate the W states with many SQUIDs (superconducting-quantum-interference-devices) in cavity QED via Raman transition. In this scheme, the transfer of quantum information between the SQUIDs and cavity is not required. And the cavity field is only virtually excited, thus the cavity decay is suppressed during the W states generation. The SQUIDs are always populated in the two ground states. Therefore, the scheme is insensitive to the spontaneous emission of the excited level of the SQUID and cavity decay.

Generation of Entangled States of Multiple Superconducting Quantum Interference Devices in Cavity

We propose a scheme for generating the maximally entangled states of many superconducting quantum interference devices (SQUIDs) by using a quantized cavity field and classical microwave pulses in cavity. In the scheme, the maximally entangled states can be generated without requiring the measurement and individual addressing of the SQUIDs.

Implementation of Deutsch–Jozsa Algorithm with Superconducting Quantum-Interference Devices via Raman Transition

In this paper, a theoretical scheme is proposed to implement the Deutsch–Jozsa algorithm with SQUIDs (superconducting quantum-interference devices) in cavity via Raman transition. The scheme only requires a quantized cavity field and classical microwave pulses. In this scheme, no transfer of quantum information between the SQUIDs and the cavity is required, the cavity field is only virtually excited and thus the cavity decay is suppressed.

One-Step Realization of SWAP Gate with Superconducting Quantum-Interference Devices and Atoms in Cavity QED

We put forward a simple scheme for one-step realization of a two-qubit SWAP gate with SQUIDs (super-conducting quantum-interference devices) in cavity QED via Raman transition. In this scheme, the cavity field is only virtually excited and thus the cavity decay is suppressed. The SWAP gate is realized by using only two lower flux states of the SQUID system and the excited state would not be excited. Therefore, the effect of decoherence caused from the levels of the SQUID system is possibly minimized. The scheme can also be used to implement the SWAP gate with atoms.