Making quantum computing scalable

Mar 20, 2009 By Miranda Marquit feature

(PhysOrg.com) -- 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 quantum computing. “By tuning the gap of a superconducting qubit, we can allow different types of coupling for use in quantum information processing,” Hans Mooij tells PhysOrg.com.

Mooij is part of a group at the Kavli Institute of Nanoscience at Delft University of Technology in The Netherlands. Along with Paauw, Fedorov and Harmans, Mooij has successfully demonstrated that such tenability is possible. The work is published in Physical Review Letters: “Tuning the Gap of a Qubit.”

“A qubit exists in two states at the same time,” Mooij explains, “and the strength of the coupling between them is the gap.” This gap represents energy splitting, and the type of qubit used by the group in Delft is known as a superconducting flux qubit. This type of qubit is needed in large quantities in order to make processing scalable. But these qubits also have to be able to couple - and decouple - in an efficient manner.

Mooij says that it is possible to strongly couple the qubits to a . “We choose to make the qubits the same frequency of the resonator. We tune this gap of the superconducting qubit to a harmonic oscillator. The qubit communicates with the oscillator while they are at the same frequency.” After a set amount of time, it is possible to then decouple the qubit from the oscillator and tune a new qubit to the frequency. Tuning is done by means of the addition of another flux loop in order to control the energy splitting. The Netherlands group found that it is possible to do this within nanoseconds - making the process very fast.

The next step, Mooij explains, is to transfer information from the resonator to another qubit. So far, the group has only shown that gap tuning is possible with one qubit, and no transfer of information has taken place. However, it should be possible for a qubit to communicate with the resonator, and then for the resonator to communicate that information to another qubit. “Any pair of qubits can be chosen for the interaction,” he points out. “If we can do it with one, as we have demonstrated, we can do it with many. But we still have not gotten any information from the resonator, and we need to take the next step.”

Tunable qubits are applicable in a number of circumstances. Being able to control the qubits’ frequencies has practical applications in terms of quantum optics and physics, as well as for quantum gates. Being able to control qubits and their coupling is a potentially large step forward in terms of technological and scientific development.

Fundamentally, Mooij says, the study of qubit tuning by resonance holds other interest. “We were happy to see that after you change the parameters, the qubit remains intact. We could not be sure of that. Study of this process, as well as its use in other experiments, could help us better understand different aspects of fundamental physics.”

More information: F. G. Paauw, A. Fedorov, C. J.P. M Harmans, and J. E. Mooij, “Tuning the Gap of a Superconducting Flux Qubit.” Physical Review Letters (2009). Available online: link.aps.org/doi/10.1103/PhysRevLett.102.090501.

Copyright 2009 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.

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

add to favorites email to friend print save as pdf

Related Stories

2 qubits in action, new step towards the quantum computer

Jun 14, 2007

Researchers at Delft University of Technology have succeeded in carrying out calculations with two quantum bits, the building blocks of a possible future quantum computer. The Delft researchers are publishing ...

Fundamental limitation to quantum computers

Jul 07, 2005

Quantum computers that store information in so-called quantum bits (or qubits) will be confronted with a fundamental limitation. This is the claim made by Dutch theoretical physicists from the Foundation for ...

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 : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

stony
not rated yet Mar 20, 2009
Are they any articles on quantum information processing noise?

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 ...