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 optics experiments can be performed in a micro-chip electrical circuit using microwaves instead of visible photons and lasers. The work is a collaboration of the laboratory of Professor Robert Schoelkopf and the theory group of Professor Steven Girvin in the Departments of Applied Physics and Physics at Yale University.

The Yale researchers have constructed a miniaturized superconducting cavity whose volume is more than one million times smaller than the cavities used in corresponding current atomic physics experiments. The microwave photon is, therefore, "trapped" allowing it to be repeatedly absorbed and reemitted by the 'atom' many times before it escapes the cavity. The 'atom' is a superconducting circuit element containing approximately one billion aluminum atoms acting in concert.

Because of the tiny cavity volume and large 'atom' size, the photon and 'atom' are very strongly coupled together and energy can be rapidly exchanged between them. Under the peculiar rules of quantum mechanics, the state of the system becomes a coherent superposition of two simultaneous possibilities: the energy is either an excitation of the atom, or it is a photon. It is this superposition that was observed in the Yale experiment.

In addition to allowing fundamental tests of quantum mechanics and quantum optics in a completely new format, this new system has many desirable features for a quantum computer. In a quantum computer the bits of information are replaced by qubits (e.g. an atom), which, paradoxically, can harness quantum uncertainty to vastly speed up certain types of calculations. The ability to couple qubits to photons, demonstrated by the Yale group, could allow qubits on a chip to be wired together via a "quantum information bus" carrying single photons.

Source: Yale University

Explore further: Scientists create first electronic quantum processor

Related Stories

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 ...

At Yale, quantum computing is a (qu)bit closer to reality

February 15, 2012

(PhysOrg.com) -- Physicists at Yale University have taken another significant step in the development of quantum computing, a new frontier in computing that promises exponentially faster information processing than the most ...

Three tiny qubits, another big step toward quantum computing

September 29, 2010

(PhysOrg.com) -- The rules that govern the world of the very small, quantum mechanics, are known for being bizarre. One of the strangest tenets is something called quantum entanglement, in which two or more objects (such ...

Progress in the fight against quantum dissipation

April 16, 2014

(Phys.org) —Scientists at Yale have confirmed a 50-year-old, previously untested theoretical prediction in physics and improved the energy storage time of a quantum switch by several orders of magnitude. They report their ...

Recommended for you

Exploring the physics of a chocolate fountain

November 24, 2015

A mathematics student has worked out the secrets of how chocolate behaves in a chocolate fountain, answering the age-old question of why the falling 'curtain' of chocolate surprisingly pulls inwards rather than going straight ...


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.