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Detection of Single Photons via Quantum Entanglement
Science & Technology

Entanglement Enhanced Detection of Single Photons

As a ‘quantum pendulum’ the ions swing in each instructions on the similar time. Illustration: IQOQI/Knabl

In a newly revealed research, physicists from the College of Innsbruck element a way to detect the scattering of a single photon on a broad optical transition with excessive sensitivity, utilizing an entangled state to amplify the tiny momentum kick an ion receives upon scattering a photon.

A crew of quantum physicists in Innsbruck led by Christian Roos and Cornelius Hempel have realized an especially delicate methodology for the spectroscopy of atomic and molecular atoms. This method can be utilized to intently research a quantity of particles. The scientists have published their findings in the journal Nature Photonics.

Virtually 200 years in the past, Bavarian physicist Joseph von Fraunhofer found darkish traces within the solar’s spectrum. It was later found that these spectral traces can be utilized to deduce the chemical composition and temperature of the solar’s environment. At this time we’re in a position to achieve details about various objects by means of mild measurements in an identical approach. As a result of usually little or no mild must be detected for this, physicists are in search of ever extra delicate spectroscopy strategies. In excessive instances, additionally single particles of mild (photons) should be measured reliably, which is technically difficult.

Thus, physicists on the Institute for Quantum Optics and Quantum Data (IQOQI) on the Austrian Academy of Sciences and the Institute for Experimental Physics of the College of Innsbruck take a detour by way of the method of quantum logic spectroscopy. It was developed some years in the past by the group of Nobel laureate David Wineland to construct extraordinarily exact atomic clocks. That is one of the primary sensible purposes of quantum info processing and, within the subsequent few years, might result in a redefinition of the second within the worldwide system of models.

Measurement by way of entanglement

Christian Roos’ and Cornelius Hempel’s crew of physicists in Innsbruck remoted single ions in an ion lure to check them below managed situations. “We don’t attempt to detect the photon that’s emitted or absorbed by an ion, however slightly the momentum kick the ion receives upon absorption or emission,” explains Cornelius Hempel. “Whereas this impact is extraordinarily small, we are able to detect it by means of quantum physics.” The physicists use an extra ‘logic’ ion, on which the measurement is carried out. “This calcium ion (40Ca+) might be managed very effectively within the experiment,” says Hempel. As spectroscopy ion the researchers use one other isotope of calcium (44Ca+).

Within the experiment a laser pulse excites the particles and entangles the digital state of the logic ion with the vibration of the particles. “On this configuration, additionally referred to as Schrödinger cat state, the ions swing like a classical pendulum in a lure. However as a ‘quantum pendulum’ they swing in each instructions on the similar time,” describes Hempel the central half of the experiment. “We then excite the ion we wish to examine by making use of totally different laser frequencies. At a sure frequency the ion emits a single photon and receives a minimal momentum kick, which causes the vibrational elements to be barely displaced. This may be noticed by means of the digital state of the logic ion. Mixed with this info, the frequency of the laser then permits us to realize details about the interior state of the spectroscopy ion.” Within the present experiment the scientists detected single photons with a likelihood of 12 %. “We, thus, show that this method works in principal. With a technically optimized set-up we will significantly enhance the sensitivity,” say Roos and Hempel confidently.

Common utility

“By utilizing the unique idea of quantum mechanical entanglement we’re in a position to achieve sensible information about single particles,” says Christian Roos excitedly. “Since our methodology of measurement doesn’t rely that a lot on the wave size of the detected photon, it could be used for varied functions,” provides Cornelius Hempel. For instance, power ranges of totally different atoms and molecules may very well be investigated through the use of this method. As a result of it’s troublesome to manage molecules in an experiment, this methodology is a gigantic progress for learning extra complicated constructions.

This analysis, carried out on the Institute for Quantum Optics and Quantum Data of the Austrian Academy of Sciences and on the Institute for Experimental Physics at Innsbruck College, was supported by the European Union.

Publication: C. Hempel, et al., “Entanglement-enhanced detection of single-photon scattering occasions,” Nature Photonics (2013); doi:10.1038/nphoton.2013.172

Picture: IQOQI/Knabl

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