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
“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
“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
Cloud technology: Dynamic certificates make cloud service providers more secure
15.01.2018 | Technische Universität München
New discovery could improve brain-like memory and computing
10.01.2018 | University of Minnesota
On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.
We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...
What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...
For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.
Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...
At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.
No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...
Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.
Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...
08.01.2018 | Event News
11.12.2017 | Event News
08.12.2017 | Event News
19.01.2018 | Materials Sciences
19.01.2018 | Health and Medicine
19.01.2018 | Physics and Astronomy