Synopsis: The quantum side of detectors

By applying environmental noise to a photon detector, researchers have identified the boundary where the device switches from a quantum device to a classical one.
Synopsis figure
V. D’Auria et al., Phys. Rev. Lett. (2011)

In quantum physics, a particle can occupy separate states at the same time, but once measured—or disturbed by the environment—it must choose a particular state in which to reside. The dynamics of this process, called decoherence, has been extensively studied over the years. Recently, physicists have investigated a process reminiscent of this phenomenon, not for a quantum state but for a measurement apparatus. A new experiment reported in Physical Review Letters has quantified how robust the quantum nature of detectors is.

Physicists have been able to characterize the quantum behavior of different photon counters by observing the detector response to a variety of photon inputs. When this data is mapped to a kind of probability distribution, some of the probabilities turn up negative, which is a telltale quantum signature.

Virginia D’Auria and her colleagues at the Kastler Brossel Laboratory in Paris, France, wanted to test the quantum limits of such photon detectors. To follow this process and observe the transition of the device from the quantum to the classical world, the researchers applied varying levels of noise to the detector. They showed that the characteristic negative probability values disappeared when the noise increased to roughly half the detector’s efficiency. – Michael Schirber


Features

More Features »

Subject Areas

Quantum InformationOptics

Previous Synopsis

Nanophysics

Nano knitting

Read More »

Next Synopsis

Related Articles

Viewpoint: Watching a Quantum Magnet Grow in Ultracold Atoms
Magnetism

Viewpoint: Watching a Quantum Magnet Grow in Ultracold Atoms

Two experiments watch an antiferromagnetic phase of matter emerge in ultracold Rydberg atoms, opening up a new platform for quantum simulation. Read More »

Viewpoint: Lost Photons Won’t Derail Quantum Sampling
Photonics

Viewpoint: Lost Photons Won’t Derail Quantum Sampling

A photon-based method for demonstrating the advantage of quantum over classical machines can handle photon loss, facilitating experiments. Read More »

Synopsis: Making Optical Fibers Immune to Bending
Optics

Synopsis: Making Optical Fibers Immune to Bending

Bending an optical fiber can distort light traveling through it, but such a distortion can be mitigated in fibers with a smoothly varying refractive-index profile.   Read More »

More Articles