Synopsis: Quantum Diamond Shines On

Diamond crystals enable new ways of storing single photons at room temperature and detecting their entanglement.
Synopsis figure
D. G. England et al., Phys. Rev. Lett. (2015)

Diamond is already a popular host material for quantum bits. Two groups have now demonstrated new ways to use diamond to build other essential elements in a quantum architecture: quantum memories and quantum repeaters. Benjamin Sussman and co-workers at the National Research Council of Canada and the Institute for Quantum Computing in Waterloo, Canada, have shown that single photons can be stored in, and retrieved from, vibrations in a diamond lattice—realizing a memory that works at room temperature and higher speed than existing schemes. And Hideo Kosaka and Naeko Niikura at the Yokohama National University, Japan, have shown that a photon can be entangled with the internal spin state of a nitrogen-vacancy defect in diamond. Their scheme could serve as a quantum repeater, a device that faithfully transfers entanglement between an incoming and an outgoing photon.

Sussman and colleagues exploit the coupling of laser light with the internal vibrations, or phonons, of diamond. Using laser sources that emit single photons, they are able to excite (“write”) and probe (“read”) such phonons. The use of phonons has two important advantages compared to other methods that are based on resonant excitation of electrons: light can be stored and retrieved at terahertz rates, and without cryogenic cooling. However, the short memory lifetime (3.5 picoseconds) will make this approach most suitable for fast computing operations, rather than long-distance communication. The scheme realized by the Yokohama group could instead offer much longer storage for quantum repeater applications: thanks to the coupling between photons and the internal states of the nitrogen vacancy, photons absorbed by the defect can generate entangled spin states. The entangled spins maintain their coherence for seconds and could be made to re-emit entangled photons for further processing.

This research is published in Physical Review Letters.

–Matteo Rini


Announcements

More Announcements »

Subject Areas

Quantum Physics

Previous Synopsis

Astrophysics

Dark Matter Not So Dark?

Read More »

Next Synopsis

Particles and Fields

Two New Particles Enter the Fold

Read More »

Related Articles

Synopsis: Tickled by a Wigner Crystal
Mesoscopics

Synopsis: Tickled by a Wigner Crystal

The lattice symmetry of a quantum Wigner crystal is deduced from its effect on quantized states in a nearby sheet of electrons. Read More »

Viewpoint: Ionization Delays That Stand Out
Optics

Viewpoint: Ionization Delays That Stand Out

Attosecond-resolution experiments have determined the delay in an electron’s emission from a molecule after being ionized with light. Read More »

Viewpoint: Liquid Light with a Whirl
Magnetism

Viewpoint: Liquid Light with a Whirl

An elliptical light beam in a nonlinear optical medium pumped by “twisted light” can rotate like an electron around a magnetic field. Read More »

More Articles