Researchers at UNIGE have demonstrated the entanglement between 16 million atoms in a crystal crossed by a single photon, confirming the theory behind the quantum networks of the future
Quantum theory is unequivocal: it predicts that a vast number of atoms can be entangled and intertwined by a very strong quantum relationship even in a macroscopic structure.
Until now, however, experimental evidence has been mostly lacking, although recent advances have shown the entanglement of 2,900 atoms. Scientists at the University of Geneva (UNIGE), Switzerland, recently reengineered their data processing, demonstrating that 16 million atoms were entangled in a one-centimetre crystal. Find out all about their research in the journal Nature Communications.
The laws of quantum physics allow to emit signals and immediately detect when they are intercepted by a third party. This property is crucial for data protection, especially in the encryption industry, which can now guarantee that customers will be aware of any interception of their messages. These signals also need to be able to travel long distances using some rather special relay devices, known as quantum repeaters: crystals whose atoms are entangled and unified by a very strong quantum relationship.
When a photon penetrates this small crystal block enriched with rare earth atoms and cooled to 270 degrees below zero (barely three degrees above absolute zero), entanglement is created between the billions of atoms it traverses. This is explicitly predicted by the theory, and it is exactly what happens as the crystal fulfils its function and re-emits -- without reading the information it has received -- in the form of a single photon.
Light analysis: the keystone of the research
It is relatively easy to entangle two particles: splitting a photon, for example, generates two entangled photons that have identical properties and behaviours. «But,» explains Florian Fröwis, a researcher in the applied physics group in UNIGE's science faculty, «it's impossible to directly observe the process of entanglement between several million atoms since the mass of data you need to collect and analyse is so huge.» As a result, Fröwis and his colleagues chose a more indirect route, pondering what measurements could be undertaken and which would be the most suitable ones.
They examined the characteristics of light re-emitted by the crystal, as well as analysing its statistical properties and the probabilities, following two major avenues: that the light is re-emitted in a single direction rather than radiating uniformly from the crystal; and that it is made up of a single photon. In this way, the researchers succeeded in showing the entanglement of 16 million atoms when previous observations had a ceiling of a few thousand.
In a parallel work, scientists at University of Calgary, Canada, demonstrated entanglement between many large groups of atoms. «We haven't altered the laws of physics,» points out Mikael Afzelius, a member of Professor Nicolas Gisin's applied physics group. «What has changed is how we handle the flow of data.»
Particle entanglement is a prerequisite for the quantum revolution that is on the horizon, which will also affect the volumes of data circulating on the networks of the future together with the power and operating mode of quantum computers. Everything, in fact, depends on the relationship between two particles at the quantum level -- a relation that is much stronger than the simple correlations proposed by the laws of traditional physics.
Two socks in the quantum world
Although the concept of entanglement can be hard to grasp, it can be illustrated using two socks! Imagine a physicist who always wears two socks of different colours. When you spot a red sock on his right ankle, you also immediately learn something about the left sock: it is not red. There is a correlation, in other words, between the two socks. This is a reasonably prosaic and quite intuitive occurrence; but when we switch to the world of quantum physics, a new type of correlation -- infinitely stronger and more mysterious -- emerges: entanglement. Now, imagine there are two physicists in their own laboratories, with a great distance separating the two. Each scientist has a quantum particle, a photon, for example.
If these two photons are in an entangled state, the physicists will see non-local quantum correlations, which conventional physics is unable to explain. They will find that the polarisation of the photons is always opposite (as with the socks in the above example), and that the photon has no intrinsic polarisation. The polarisation measured for each photon is, therefore, entirely random and fundamentally indeterminated before being measured. What we are dealing with here is an unsystematic phenomenon that occurs simultaneously in two locations that are far apart... and this is the mystery of quantum correlations!
Florian Fröwis | EurekAlert!
From Hannover around the world and to the Mars: LZH delivers laser for ExoMars 2020
21.11.2017 | Laser Zentrum Hannover e.V.
Taking a spin on plasma space tornadoes with NASA observations
20.11.2017 | NASA/Goddard Space Flight Center
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
20.11.2017 | Earth Sciences
20.11.2017 | Earth Sciences
20.11.2017 | Life Sciences