arXiv subjects

Ryszard Tanaś

Publications and source records attributed to Ryszard Tanaś.

5 recordsLinked to original sources

arXiv2019

Creating a switchable optical cavity with controllable quantum-state mapping between two modes

We describe how an ensemble of four-level atoms in the diamond-type configuration can be applied to create a fully controllable effective coupling between two cavity modes. The diamond-type configuration allows one to use a bimodal cavity that supports modes of different frequencies or different circular polarisations, because each mode is coupled only to its own transition. This system can be used for mapping a quantum state of one cavity mode onto the other mode on demand. Additionally, it can serve as a fast opening high-Q cavity system that can be easily and coherently controlled with laser fields.

quant-ph↗

arXiv2012

Evolution of quantum correlations in a two-atom system

We discuss the evolution of quantum correlations for a system of two two-level atoms interacting with a common reservoir. The Markovian master equation is used to describe the evolution of various measures of quantum correlations.

quant-ph↗

arXiv2009

High-fidelity atomic-state teleportation protocol with non-maximally-entangled states

We propose a protocol of the long-distance atomic state teleportation via cavity decay, which allows for high-fidelity teleportation even with currently available optical cavities. The protocol is based on the scheme proposed by Bose \emph{et al.} [Phys. Rev. Lett. {\textbf{83}}, 5158 (1999)] but with one important modification: it employs non-maximally-entangled states instead of maximally entangled states.

quant-ph↗

arXiv2008

Fine tuning of quantum operations performed via Raman transitions

A scheme for fine tuning of quantum operations to improve their performance is proposed. A quantum system in $Λ$ configuration with two-photon Raman transitions is considered without adiabatic elimination of the excited (intermediate) state. Conditional dynamics of the system is studied with focus on improving fidelity of quantum operations. In particular, the $π$ pulse and $π/2$ pulse quantum operations are considered. The dressed states for the atom-field system, with an atom driven on one transition by a classical field and on the other by a quantum cavity field, are found. A discrete set of detunings is given for which high fidelity of desired states is achieved. Analytical solutions for the quantum state amplitudes are found in the first order perturbation theory with respect to the cavity damping rate $κ$ and the spontaneous emission rate $γ$. Numerical solutions for higher values of $κ$ and $γ$ indicate a stabilizing role of spontaneous emission in the $π$ and $π/2$ pulse quantum operations. The idea can also be applied for excitation pulses of different shapes.

quant-ph↗

arXiv2007

Improving fidelity in atomic state teleportation via cavity decay

We propose a modified protocol of atomic state teleportation for the scheme proposed by Bose et al. (Phys. Rev. Lett. 83, 5158 (1999)). The modified protocol involves an additional stage in which quantum information distorted during the first stage is fully recovered by a compensation of the damping factor. The modification makes it possible to obtain a high fidelity of teleported state for cavities that are much worse than that required in the original protocol, i.e., their decay rates can be over 25 times larger. The improvement in the fidelity is possible at the expense of lowering the probability of success. We show that the modified protocol is robust against dark counts.

quant-ph↗