The concepts of quantum technology promise to achieve more
powerful information processing than is possible with even the best possible
classical computers. To actually build efficient quantum computers remains a
significant challenge in practice. A new scheme termed “coherent photon
conversion,” could potentially overcome all of the currently unresolved
problems for optical implementations of quantum computing. The international
team of scientists led by researchers from the Vienna
Center for Quantum Science and
Technology (VCQ) at the University
of Vienna (group of Anton
Zeilinger) introduces this new scheme in Nature.
A new way for photons
Quantum technology derives its potential by exploiting uniquely quantum
features such as superposition and entanglement. Single photons are excellent
quantum information carriers, because they are naturally almost perfectly
isolated from their environment. Also, quantum computers based on photons
promise to be extremely fast. But current schemes for preparing, processing and
measuring photons are inefficient.
The new scheme provides a method of coherent
conversion between different photon states and is based on enhancing the
nonlinearity of a medium by a strong laser field. The method paves a road to
solving all open challenges for optical quantum computation. For example,
deterministically doubling single photons solves the preparation and measuring
problems, and a novel type of photon-photon interaction gives efficient quantum
gates. This new quantum optics toolbox opened up by “coherent photon
conversion” promises to lead to a nonlinear optical quantum computer.
First experiments
In a first series of experiments the group uses photons and highly non-linear
glass fibers for a proof-of-principle demonstration of a process suitable for
implementing the scheme. While deterministic operation has yet to be achieved,
the authors’ results suggest a line for development how this might be possible
with sophisticated optical technologies, such as using highly nonlinear glasses
and stronger lasers. Interestingly, the general idea of “coherent photon
conversion” can also be applied to various other physical systems like atoms or
nanomechanical devices.
