Optical Switching via Quantum Interference Effects in a Multilevel Atomic System

Jianhua Yang, Shi Yao Chong, Jian Qi Shen +3 more

A large number of novel semiclassical and quantum optical effects and phenomena (e.g., coherent population trapping, electromagnetically induced transparency, spontaneous emission inhibition and lasing without population inversion) caused by atomic multi-level phase coherence can be found in three- and four-level atomic vapor media. Such phase coherence includes destructive and constructive quantum interference among various pathways of transition in the atomic systems. Since a simple RLC electric circuit can be used to simulate some resonant responses of a two-level atomic system (or two-state resonant systems), we will consider an analog of interference effect (phase coherence) in an electric circuit containing three RLC meshes for mimicking three- and four-level atomic systems. If certain magnitudes of capacitance and inductance parameters are chosen (or the capacitance and inductance are tuned), the destructive and constructive interference among currents in the circuit can be switched to each other. Thus, the analog of nearly all the quantum coherent effects relevant to a multi-level atomic system that interacts with optical fields can in principle be realized in the present multi-mesh RLC circuit.

Mostafa Sahrai, Seyyed Hossein Asadpour, Hamed Mahrami +1 more

J.Q. Shen

Abstract Multilevel quantum coherence and its quantum‐vacuum counterpart, where a three‐level dark state is involved, are suggested in order to achieve new photonic and quantum optical applications. It is shown that such a three‐level dark state in a four‐level tripod‐configuration atomic system consists of three lower levels, where constructive and destructive quantum interference between twocontroltransitions (driven by twocontrolfields) arises. We point out that the controllable optical response due to the double‐controltunablequantum interference can be utilized to design some fascinating new photonic devices such as logic gates, photonic transistors and switches at quantum level. A single‐photon two‐input XOR logic gate (in which the incident “gate” photons are the individual light quanta of the two control fields) based on such an effect of optical switching control with an EIT (electromagnetically induced transparency) microcavity is suggested as an illustrative example of the application of thedark‐state manipulationvia thedouble‐control quantum interference. The present work would open up possibility of new applications in both fundamental physics (e.g., field quantization and relevant quantum optical effects in artificial systems that can mimic atomic energy levels) and applied physics (e.g., photonic devices such as integrated optical circuits at quantum level).

Ravi Kumar, Vandna Gokhroo, Síle Nic Chormaic

Ultrathin optical fibres integrated into cold atom setups are proving to be ideal building blocks for atom-photon hybrid quantum networks. Such optical nanofibres (ONFs) can be used for the demonstration of nonlinear optics and quantum interference phenomena in atomic media. Here, we report on the observation of multilevel cascaded electromagnetically induced transparency (EIT) using an optical nanofibre to interface cold 87 Rb atoms. Intense evanescent fields can be achieved at ultralow probe (780 nm) and coupling (776 nm) powers when the beams propagate through the nanofibre. The observed multipeak transparency spectra of the probe beam could offer a method for simultaneously slowing down multiple wavelengths in an optical nanofibre or for generating ONF-guided entangled beams, showing the potential of such an atom-nanofibre system for quantum information. We also demonstrate all-optical-switching in the all-fibred system using the obtained EIT effect.

Nguyen Tuan Anh, Thai Doan Thanh, Nguyen Huy Bang +1 more