A new kind of quantum computer

November 6, 2017
A photograph of D-Wave's 1000+ qubit computer chip under development. CfA scientists and their colleagues have proposed a new way to use photons of light instead of silicon chips as qubits, opening the door to new technologies. Credit: Google

Quantum mechanics incorporates some very non-intuitive properties of matter. Quantum superposition, for example, allows an atom to be simultaneously in two different states with its spin axis pointed both up and down, or combinations in between. A computer that uses quantum mechanical manipulation of atoms or particles therefore has many more possible options than a conventional one that works with "zeros" and "ones" and has only two choices, called bits. A quantum computer's memory uses instead what are called quantum bits - qubits - and each qubit can be in a superposition of these two states. As a result, theoretical physicists estimate a quantum computer with only about one hundred of these qubits could in principle exceed the computing power of the powerful current classical computers. Building a quantum computer is therefore one of the main technological goals in modern physics and astrophysics.

CfA physicist Hannes Pichler, of the CfA's Institute for Theoretical Atomic, Molecular and Optical Physics (ITAMP), and three colleagues have proposed a new way to build a quantum computer using just a single atom. Light quanta (photons) can be used as information carriers and act as qubits, but to use them in a quantum computer they must interact with each other.

Under normal conditions, however, light does not interact with itself and so the challenge is to create correlations between them. The key idea of their new paper is to allow light photons from an atom to interact with their own mirror image reflections. Photons that the atom emits are reflected by the mirror and can interact again with the atom but with a very slight time delay. That delay, the scientists show, results in the combined waveform of the photons being so complex that in principle any quantum computation can be achieved by simply measuring the emitted photons.

The theoretical discovery is not only a conceptual breakthrough in optics and information, it opens the door to new technology. In particular, the proposed single atom setup is appealing since it minimizes the resources needed and relies only on elements that have already been demonstrated in state-of the-art experiments.

Explore further: Researchers take a step toward quantum mechanical analysis of plant metabolism

More information: Hannes Pichler et al. Universal photonic quantum computation via time-delayed feedback, Proceedings of the National Academy of Sciences (2017). DOI: 10.1073/pnas.1711003114

Related Stories

How quantum mechanics can change computing

August 24, 2017

In early July, Google announced that it will expand its commercially available cloud computing services to include quantum computing. A similar service has been available from IBM since May. These aren't services most regular ...

Yale scientists bring quantum optics to a microchip

September 8, 2004

A report in the journal Nature describes the first experiment in which a single photon is coherently coupled to a single superconducting qubit (quantum bit or "artificial atom"). This represents a new paradigm in which quantum ...

Scientists track quantum errors in real time

July 14, 2014

(Phys.org) —Scientists at Yale University have demonstrated the ability to track real quantum errors as they occur, a major step in the development of reliable quantum computers. They report their results in the journal ...

Recommended for you

Single-photon detector can count to four

December 15, 2017

Engineers have shown that a widely used method of detecting single photons can also count the presence of at least four photons at a time. The researchers say this discovery will unlock new capabilities in physics labs working ...

Real-time observation of collective quantum modes

December 15, 2017

A cylindrical rod is rotationally symmetric - after any arbitrary rotation around its axis it always looks the same. If an increasingly large force is applied to it in the longitudinal direction, however, it will eventually ...

A shoe-box-sized chemical detector

December 15, 2017

A chemical sensor prototype developed at the University of Michigan will be able to detect "single-fingerprint quantities" of substances from a distance of more than 100 feet away, and its developers are working to shrink ...

An ultradilute quantum liquid made from ultra-cold atoms

December 14, 2017

ICFO researchers created a novel type of liquid 100 million times more dilute than water and 1 million times thinner than air. The experiments, published in Science, exploit a fascinating quantum effect to produce droplets ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.