Physicists propose quantum refrigerator

Sep 01, 2010 by Lin Edwards report

( -- Scientists at the University of Bristol in the UK have proposed a refrigerator that consists of just a few quantum particles -- qubits.

Theoretical physicists Noah Linden, Paul Skrzypczyk, and Sandu Popescu, report in the upcoming they can in principle make a thermal engine or using a few qubits, which are with only two possible states: an excited state with fixed energy, and a ground state with zero energy. The researchers have found a way to draw energy out of one of the qubits to cool the third.

The idea of making a thermal machine began in 1824 with the theories of Sadi Carnot, a French engineer who imagined a gas-filled piston brought into contact with either a hot or cold body or 'bath'. In one cycle the piston does work, the gas expands, and heat is absorbed when in contact with the hot bath, and the gas is compressed and releases heat when in contact with the cold bath. If this cycle is reversed, in response to work done on it, the piston absorbs heat from the cold bath and releases it into the hot bath.

In the current theoretical situation three linked qubits are used, two forming the refrigerator, and the third being the object to be cooled. Applying Carnot's ideas to the , they expose one of the refrigerator qubits to a cold 'bath' (actually ) and the other to a hot bath. The heated qubit absorbs energy and flips into its excited state, and because the qubits have a quantum connection, they influence each other, resulting in the cold qubit siphoning off energy from the third qubit and cooling it. The energy absorbed by the second qubit then dissipates.

Linden and his team calculate that as the hottest heats up the refrigerator's ability to cool increases. He said that once the system is set up it can run forever as long as the hot bath stays hot. It could in theory cool to near .

The three qubits have eight possible states (000, 010, 100, 101, and so on, where 0 = ground state and 1 = ), but this can be reduced to six if the second and third qubits are replaced by one qutrit, which is a particle with a zero energy ground state and two excited states. To use a qutrit in the refrigerator these two states would have to be in contact with baths at different temperatures. Linden said the group believes this would be the smallest thing you could possibly term a refrigerator.

Popescu said it may be possible to make a quantum refrigerator using trapped ions for the qubits, and the hot and cold baths could be provided by streams of laser light. This may allow researchers planning to use qubits in a quantum computer to cool some of the qubits using others. The next step in the research is to collaborate with other scientists to design and actually build a quantum refrigerator.

Apart from quantum computers other possible applications include cooling parts of proteins within cells to regulate the speed of their reactions.

Explore further: Physicists design quantum switches which can be activated by single photons

More information: The abstract of the upcoming PRL paper "How small can thermal machines be? The smallest possible refrigerator" can be viewed at .

Related Stories

Creating a six-qubit cluster state

Nov 02, 2009

( -- Many scientists believe that quantum entanglement is required in order for effective quantum computing. Entanglement takes place when there is a connection that exists between two objects - even when they ...

Making quantum computing scalable

Mar 20, 2009

( -- Quantum information processing is one of the hottest areas of science and technology right now. Making quantum information processing scalable is an important part of the efforts involved with regard to practical ...

Straightening messy correlations with a quantum comb

Nov 23, 2009

Quantum computing promises ultra-fast communication, computation and more powerful ways to encrypt sensitive information. But trying to use quantum states as carriers of information is an extremely delicate ...

Using degrees of freedom to get hyperentanglement

Jan 27, 2010

( -- One of the biggest challenges scientists are grappling with today is the creation of an efficient quantum computer. There are a number of models out there, and hundreds of scientists and researchers around ...

Yale scientists bring quantum optics to a microchip

Sep 08, 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 ...

Recommended for you

Could 'Jedi Putter' be the force golfers need?

Apr 18, 2014

Putting is arguably the most important skill in golf; in fact, it's been described as a game within a game. Now a team of Rice engineering students has devised a training putter that offers golfers audio, ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Sep 01, 2010
Would this be useful low-energy ion rings for Colliders?
not rated yet Sep 01, 2010
Uh, what? Is this as silly as it seems or am I missing something? Correlated quantum particles cannot affect each other that way. Sure, there is a strange non classical correlation. But you cannot use this to control them. And once they interact with the environment there isn't even any correlation.

Someone please explain this to me.

More news stories

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...