Quantum computing nears with European QAP project

it works only over short distances. EU-funded QAP hopes to develop a quantum repeater that can maintain entanglement over large distances. It has already had considerable success up to the 200km range, and growing.

Ideal information carrier
Maintaining entanglement over long distances — so essential to QKD, but also communications and networks — is the most immediate and compelling application in the QAP programme, but it is far from the only one. Many other areas of work show signs of progress, too. Storage and memory are essential for quantum computing. It is not too difficult to encode a piece of information on a photon, which is an ideal information carrier because of its high speed and weak interaction with the environment.

It is difficult to store that information for any length of time, so QAP is developing ways of transferring quantum information from photons to and from atoms and molecules for storage, and the project is making steady progress.

Similarly, QAP’s work to develop quantum networks is progressing well. One team within the overall research effort has managed to develop a reliable way to calibrate and test detectors, a prime element in the network system.

“This is important because it will be essential to develop reliable methods to test results if work on quantum networks is to progress,” notes Walmsley. The research group has submitted a patent application for this work.

Stimulating simulation
Quantum simulation, too, offers some tantalizing opportunities. The primary goal of QAP’s Quantum Simulations and Control subproject is to develop and advance experimental systems capable of simulating quantum systems whose properties are not approachable on classical computers. Imagine, for example, trying to model superconducting theory. It is hugely complex, and classic computers are quickly overwhelmed by the size of the problem. Quantum methods, however, are inherently capable of dealing with far greater complexity because of the nature of the qubit, or quantum bit. Classical, digital bits operate on the basis of on or off, yes or no. Quantum bits can be yes, no, or both. It takes classical computing from 2D into the 3D information world.

One could say that while classical computers attack problems linearly, quantum computers attack problems exponentially. As a result, with just a few qubits, it is possible to do incredibly large computations, and that means that quantum simulation of complex problems could be a medium-term application.

“We are not saying we will solve all the problems in the area of simulation, but we will make a good start,” warns Walmsley. That defines QAP nicely: a kick-start for quantum applications in Europe. The QAP project received funding from the ICT strand of the EU’s Sixth Framework Program for research.