Synopsis: Cavities Play Catch with Photons

A single photon with an optimally shaped waveform can be loaded into a cavity with near-unity efficiency.
Synopsis figure
Luwei Zhao/The Hong Kong University of Science and Technology

Future quantum networks might consist of flying quantum bits made of single photons, captured by nodes that perform computations and send messages. But how easy is it to catch and hold a single photon, for instance, in a small cavity? Researchers in the group of Shengwang Du at the Hong Kong University of Science and Technology have demonstrated that, by shaping its wave function, an individual photon can be loaded into a cavity with near-unity efficiency.

When a photon is injected into a cavity, it can be reflected, transmitted, or captured by the cavity. In previous experiments, reflection and transmission limited the photon loading efficiency to 20%. The new idea is based on exploiting quantum interference phenomena in a cavity between two mirrors—a perfectly reflecting one and an input/output mirror. Using an electro-optical modulator, the researchers prepare a photon wave function that, after each round trip in the cavity, interferes destructively with the reflected wave packet. This eliminates most reflections from the cavity while the photon is injected into the cavity.

To monitor the cavity photon without perturbing it, the authors apply a “heralded” scheme: a laser-pumped rubidium-atom cloud emits entangled photon pairs, which are then split. The detection of one photon heralds the presence of the one being sent into the cavity. Using an optimally prepared waveform, the authors demonstrate a record loading efficiency of 87%. The scheme could be used to build nodes of a network based on cavity quantum electrodynamics, in which operations are carried out via the interaction of a single photon with a single atom.

This research is published in Physical Review Letters.

–Matteo Rini


Features

More Features »

Announcements

More Announcements »

Subject Areas

OpticsQuantum Physics

Previous Synopsis

Next Synopsis

Atomic and Molecular Physics

One Very Cold Atom

Read More »

Related Articles

Viewpoint: Inducing Transparency with a Magnetic Field
Optics

Viewpoint: Inducing Transparency with a Magnetic Field

A magnetic field applied to an atomic sample in an optical cavity generates optical transparency that could be used to enhance the frequency stability of lasers. Read More »

Focus: <i>Image</i>—Honeycomb Diffraction
Photonics

Focus: Image—Honeycomb Diffraction

Predictions of diffraction patterns for honeycomb photonic crystals were part of a comprehensive study of these structures that may be useful in nanoscale photonic devices. Read More »

Synopsis: Laser Stars Under the Lens
Astrophysics

Synopsis: Laser Stars Under the Lens

Raman scattering could contaminate astronomical observations that use artificial, laser-generated “stars” to correct for the effect of atmospheric turbulence. Read More »

More Articles