Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Analogue logic for quantum computing

22.02.2008
Digital logic, or bits, is the only paradigm for the IT world, and up to now researchers used it almost exclusively to study quantum information processing. But European scientists, in a series of firsts, have proved that an analogue approach is far easier in the quantum world.

Modern computing is digital, a series of 1s and 0s that, once combined, create powerful information processing systems. The system is so simple – on or off, yes or no – that it almost seems dumb. It is that very simplicity that gives digital computing its power. It works very well.

But we have a problem. Silicon circuits are getting so small that they will soon be bumping up against a fundamental physical limit.

“We know very well that, as the miniaturisation of computers continues, at some point the carriers of information will have a size that approaches that of atoms,” warns Nicolas Cerf, coordinator of the Covaqial project. “As classical physics becomes inapplicable, we will have to look at quantum mechanics for our future information processing systems.”

And that is exactly what quantum scientists have been doing for the last 20 years. Essentially, they have been attempting to reproduce the classical, digital, computer of 1s and 0s in the microscopic world by using particles to carry information as quantum bits, or qubits. Up to now, it really was the only game in quantum town.

Logic, but not as we know it
But this is changing. Covaqial led the charge for a new type of quantum information processing when it began four years ago. It looked at an analogue logic paradigm for the quantum world, using continuous variables instead of 1s and 0s.

“In classical computing, there have been attempts to create an analogue logic, but no major success,” notes Cerf. “But it turns out, for a variety of reasons, that using an analogue approach, like continuous variables, might work very well in quantum computing. We felt it was a promising approach, so that is why we started up Covaqial.”

Unlike qubits, where one atom or particle carries the information, continuous variables (CV) use an ensemble of atoms or photons to carry the information – the first with matter and the second with light.

Both digital and analogue approaches to quantum information science use the peculiar properties of quantum particles as the ‘signifier’ of the information carried, such as the spin of a single electron or the polarisation of a photon for qubits, or the analogue properties of a group of electrons or photons for CV.

“It is the collective property of this group of electrons, or photons, that becomes the information carrier in CV. When you have this many particles you can call it continuous even though there are many very small steps in the information-encoding variable,” relates Cerf.

The upshot, though, and what makes CV interesting, is that it is much easier to manipulate, control and experiment with than individual particles. Quantum teleportation using qubits, for example, was described in the early 1990s and proved experimentally five years later. In contrast, teleportation with CV was proved experimentally just one year after it was theorised. All because CVs are much easier to use.

Cat out of the bag
The field looked promising, and after a series of spectacular results Covaqial proved that CV could provide elegant solutions to some of the fundamental issues affecting quantum information processing.

“We achieved the first major result after less than one year. It was an experiment demonstrating quantum memory,” explains Cerf. “It’s like classical memory, so it is really a prerequisite for the field.”

The team demonstrated memory for a light pulse stored in an atomic ‘ensemble’ during one millisecond using CV. It might not sound like much, but remember light travels several hundred kilometres in that time. Even if looped in an optical fibre, the energy is so delicate that it would disappear in well under a millisecond. They did this at room temperature, whereas atomic qubits generally need to be super-cooled.

The second result created an optical ‘Schroedinger’s cat’. Schrödinger’s cat was a thought experiment that illustrated how objects can have two distinct states at the same time, in this case a dead cat and a live cat.

Covaqial created a light pulse – an ensemble of photons – simultaneously in two states. “It is very important for the development of a quantum repeater, which will allow quantum communications to extend to much further distances,” Cerf reveals.

Finally, for the first time ever, an experiment demonstrated interspecies quantum teleportation. Teleportation occurs where the state of one particle is moved onto another particle. “It had been done before with photons or atoms, but this is the first time it worked from photons to atoms. These were our most impressive results, but we had many more,” notes Cerf.

As a result of their work, CVs are now a hot topic in quantum information processing, and Covaqial propelled Europe to leadership in the field. Now, the team will continue their work in a new European Commission project, COMPAS, starting in a few months.

“Strictly speaking, Covaqial was about quantum communication, but all the results will be essential for the development of quantum computing,” explains Cerf. “COMPAS will attack directly the challenges of quantum information processing using CVs.”

Further helping to usher in the era of the analogue quantum computer.

Christian Nielsen | alfa
Further information:
http://cordis.europa.eu/ictresults/index.cfm/section/news/tpl/article/id/89537

More articles from Information Technology:

nachricht Reversing cause and effect is no trouble for quantum computers
20.07.2018 | Centre for Quantum Technologies at the National University of Singapore

nachricht Study suggests buried Internet infrastructure at risk as sea levels rise
18.07.2018 | University of Wisconsin-Madison

All articles from Information Technology >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>