In a recently
published article in Science, Prof. Roberto Morandotti and his team demonstrate
the generation
of complex entangled quantum states on an optical chip, bringing us one step
closer to
practical applications in quantum information processing. Left: On-chip
frequency combs
for scalable,
complex quantum state generation. Top
right: Quantum frequency comb of entangled photons.
Bottom right: Photonic chip
– compatible with common semiconductor fabrication technologies.
Credits :
Ultrafast Optical Processing Group, 2016.
(March 11, 2016) Quantum
communications and computing
The optical chip developed at INRS by Prof. Roberto
Morandotti’s team overcomes a number of obstacles in the development of quantum
computers, which are expected to revolutionize information processing. The
international research team has demonstrated that on-chip quantum frequency
combs can be used to simultaneously generate multiphoton entangled quantum bit
(qubit) states.
Quantum computing differs fundamentally from classical
computing, in that it is based on the generation and processing of
qubits.Unlike classical bits, which can have a state of either 1 or 0, qubits
allow a superposition of the 1 and 0 states (both simultaneously).Strikingly,
multiple qubits can be linked in so-called ‘entangled’ states, where the
manipulation of a single qubit changes the entire system, even if individual
qubits are physically distant.This property is the basis for quantum
information processing, aiming towards building superfast quantum computers and
transferring information in a completely secure way.
Professor Morandotti has focused his research efforts on the
realization of quantum components compatible with established technologies.The
chip developed by his team was designed to meet numerous criteria for its
direct use:it is compact, inexpensive to make, compatible with electronic
circuits, and uses standard telecommunication frequencies.It is also scalable,
an essential characteristic if it is to serve as a basis for practical
systems.But the biggest technological challenge is the generation of multiple,
stable, and controllable entangled qubit states.
The generation of qubits can rely on several different
approaches, includingelectron spins, atomic energy levels, and photon quantum
states. Photons have the advantage of preserving entanglement over long
distances and time periods.But generating entangled photon states in a compact
and scalable way is difficult.“What is most important, several such states have
to be generated simultaneously if we are to arrive at practical applications,”
added INRS research associate Dr. Michael Kues.
Roberto Morandotti’s team tackled this challenge by using
on-chip optical frequency combs for the first time to generate multiple
entangled qubit states of light.As Michael Kues explains, optical frequency
combs are light sources comprised of many equally-spaced frequency
modes.“Frequency combs are extraordinarily precise sources and have already
revolutionized metrology and sensing, as well as earning their discoverers the
2005 Nobel Prize in Physics.”
Thanks to these integrated quantum frequency combs, the chip
developed by INRS is able to generate entangled multi-photon qubit states over
several hundred frequency modes.It is the first time anyone has demonstrated
the simultaneous generation of qubit multi-photon and two-photon entangled
states:Until now, integrated systems developed by other research teams had only
succeeded in generating individual two-photon entangled states on a chip.