Compiled by EuroPhotonics staff
Quantum circuits based on optical multimode
interference (MMI) are being used to advance quantum computers.
Building a quantum computer requires a large number of interconnected
components, or gates, whose function is similar to that of a microprocessor in a
personal computer. The quantum gates of today are large structures that often are
too bulky to be scaled to the large, complex circuits required for practical applications.
Now, scientists at the University of Bristol’s Centre for
Quantum Photonics have discovered that quantum information can be manipulated with
integrated photonic circuits. These circuits are compact – enabling scalability
– and stable – with low noise – and soon could be mass-produced
for quantum computers.
The team collaborated with a scientist at Imperial College London
to show a new class of integrated divides that promises further reduction in the
number of components that will be used for building future quantum circuits. The
devices, based on optical MMIs, have been widely used in classical optics because
of their compact and robust nature, suitable for fabrication tolerance.
Until now, it had not been clear how the devices would work in
the quantum regime. The researchers demonstrated that MMIs can perform quantum interference at the high fidelity required. Their findings appeared in the March 1, 2011, issue of Nature Communications (doi: 10. 1038/ ncomms1228).
Scientists now will be able to implement more compact photonic
circuits for quantum computing. MMIs can generate large entangled states, at the
heart of the exponential speedup promised by quantum computing. The researchers
expect that applications will range from new circuits for quantum computation to
ultraprecise measurement and secure quantum communication.