Predictions from quantum physics have been confirmed by countless experiments, but no one has yet detected the quantum physical effect of entanglement directly with the naked eye. This should now be possible thanks to an experiment proposed by a team around a theoretical physicist at the University of Basel. The experiment might pave the way for new applications in quantum physics.
Quantum physics is more than 100 years old, but even today is still sometimes met with wonderment. This applies, for example, to entanglement, a quantum physical phenomenon that can be observed between atoms or photons (light particles): when two of these particles are entangled, the physical state of the two particles can no longer be described independently, only the total system that both particles form together.
Despite this peculiarity, entangled photons are part of the real world, as has been proven in many experiments. And yet no one has observed entangled photons directly. This is because only single or a handful of entangled photons can be produced with the available technology, and this number is too low for the human eye to perceive these photons as light.
Entangled photons amplified 100-fold
Nicolas Sangouard, a theoretical physicist at the University of Basel, together with two quantum physicists from Delft, Netherlands, and Innsbruck, Austria, has now shown in the scientific journal Optica how it may be possible to detect entangled photons directly. The basic idea of the experiment is that an entangled photon is generated and then amplified using a special technique, without destroying the quantum physical entanglement.
In the process, about 100 entangled photons are present, which, according to current knowledge, is the precise number needed to create the impression of light in humans. But although hundreds of photons reach the retina, there are also significant losses: only about seven actually reach one of the 120 million light-detecting rods of the retina. These photons then generate the nerve impulse that triggers the perception of light in the brain.
Two entangled states
In the experiment proposed by the three quantum physicists, entanglement is created by a single photon directed at a semi-transparent mirror. Sangouard explains what happens next: “The single photon is not transmitted or reflected by the mirror; instead – quantum physics is strange – the photon is simultaneously transmitted and reflected. Behind the mirror, the photon exists in a ‘transmitted’ and ‘reflected’ state, whereby these two states are entangled with another.”
A photon detector and a human observer are placed behind the mirror. In order for the observer’s eye to detect the entangled photons, they are amplified 100-fold with a type of magnifying glass before they reach the eye. Technically speaking, this is achieved by a displacement in phase space using a laser. Whether the human observer and/or the detector actually detect the entangled photons is not revealed directly but rather through determination of the probabilities. For this, the experiment is repeated many times and the data obtained statistically analyzed.
Very long observation period
It is not yet certain if Sangouard’s group will conduct the experiment or if other quantum physicists will implement it. The required technologies – special photon sources and special lasers – are generally available today; however, the biggest obstacle is the practical implementation of the experiment. The human eye is about a billion times slower at counting weak light pulses than modern photon detectors. “According to an initial estimate, several hundreds of thousands of runs would be necessary until we have enough data to determine if we’ve actually detected entangled photons. This means that the test person in our experiment would have to note at one-second intervals over the course of several hundreds of hours if they have just detected a light pulse or not.”
If these obstacles were overcome, the experiment would demonstrate that the human eye is able to detect quantum entanglement directly and achieve what until now has required complicated and expensive detectors. Scientists are currently working to use the principle of entanglement to build secure digital communication links and for quantum computers. According to Sangouard, these applications could benefit from the new experiment.
The research project is supported by the Swiss National Science Foundation as part of the National Center of Competence in Research in Quantum Science and Technology (NCCR-QSIT) and the John Templeton Foundation in the US.
Valentina Caprara Vivoli, Pavel Sekatski, and Nicolas Sangouard
What does it take to detect entanglement with the human eye?
Optica (2016), doi: 10.1364/optica.3.000473
Prof. Dr. Nicolas Sangouard, University of Basel, Department of Physics, tel. +41 61 267 39 15, email: email@example.com
Reto Caluori | Universität Basel
Further Improvement of Qubit Lifetime for Quantum Computers
09.12.2016 | Forschungszentrum Jülich
Electron highway inside crystal
09.12.2016 | Julius-Maximilians-Universität Würzburg
Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.
Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
09.12.2016 | Life Sciences
09.12.2016 | Ecology, The Environment and Conservation
09.12.2016 | Health and Medicine