A Visible Light Photon Counter (VLPC) is a

photon counting Photon counting is a technique in which individual photons are counted using a single-photon detector (SPD). A single-photon detector emits a pulse of signal for each detected photon, in contrast to a normal photodetector, which generates an analo ...

photodetector Photodetectors, also called photosensors, are sensors of light or other electromagnetic radiation. There is a wide variety of photodetectors which may be classified by mechanism of detection, such as photoelectric or photochemical effects, or ...

based on impurity-band conduction in

arsenic Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, ...

- doped silicon. They have high quantum efficiency and are able to detect single

photon A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they a ...

s in the visible range of the electromagnetic spectrum. The ability to count the exact number of photons detected is extremely important for

quantum key distribution Quantum key distribution (QKD) is a secure communication method which implements a cryptographic protocol involving components of quantum mechanics. It enables two parties to produce a shared random secret key known only to them, which can then b ...

. Rockwell International's Science Center had previously announced the "Solid-State Photomultiplier" (SSPM), a wide-band (0.4–28 µm) detector.M.D. Petroff, M.G. Stapelbroek and W.A. Kleinhans: "Detection of Individual 0.4–28 μm Wavelength Photons via Impurity‐Impact Ionization in a Solid‐State Photomultiplier" ''Applied Physics Letters'' 51(6) pp.406-408 (1987) In the late 1980s a collaboration – initially consisting of Rockwell and

UCLA The University of California, Los Angeles (UCLA) is a public land-grant research university in Los Angeles, California. UCLA's academic roots were established in 1881 as a teachers college then known as the southern branch of the California ...

– began developing scintillating-fiber particle trackers for use at the

Superconducting Super Collider The Superconducting Super Collider (SSC) (also nicknamed the desertron) was a particle accelerator complex under construction in the vicinity of Waxahachie, Texas. Its planned ring circumference was with an energy of 20 TeV per proton and was ...

,M.D. Petroff and M. Atac: "High Energy Particle Tracking Using Scintillating Fibers and Solid State Photomultipliers" ''IEEE Transactions on Nuclear Science'' 36(1) pp.163-164. (1989)M. Atac: "Scintillating Fiber Tracking at High Luminosities using Visible Light Photon Counter Readout" pp.149-160 in ''Imaging Detectors In High Energy, Astroparticle And Medical Physics - Proceedings Of The UCLA International Conference'', J. Park (''ed.''), World Scientific Publishing (1996) based on a dedicated variant of the SSPM that came to be known as the Visible Light Photon Counter.B. Abbot ''et al.'': "Studies of Visible Light Photon Counters with Fast Preamplifiers" ''Conference Record of the 1991 IEEE Nuclear Science Symposium and Medical Imaging Conference'', Santa Fe, NM, USA, pp.369-373 (1991) The operating principles are similar to APDs but based on impurity-band conduction. The devices are made from

- doped silicon and have an impurity band 50 meV below the conduction band, resulting in a gain of to at a

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of only a few volts (e.g. 7 V).In contrast, SPADs require a high

voltage and consequent quenching of the output current. The narrow

bandgap In solid-state physics, a band gap, also called an energy gap, is an energy range in a solid where no electronic states can exist. In graphs of the electronic band structure of solids, the band gap generally refers to the energy difference (i ...

reduces gain dispersion, resulting in a uniform response to each photon, and hence the output pulse height is proportional to the number of incident photons. VLPCs must operate at cryogenic temperatures (6–10 K).M.D. Petroff and M.G. Stapelbroek: "Photon-Counting Solid-State Photomultiplier" ''IEEE Transactions on Nuclear Science'' 36(1) pp.158-162. . (1989) They have a quantum efficiency of 85% at 565 nm and a

temporal resolution Temporal resolution (TR) refers to the discrete resolution of a measurement with respect to time. Physics Often there is a trade-off between the temporal resolution of a measurement and its spatial resolution, due to Heisenberg's uncertainty p ...

of several

nanoseconds A nanosecond (ns) is a unit of time in the International System of Units (SI) equal to one billionth of a second, that is, of a second, or 10 seconds. The term combines the SI prefix ''nano-'' indicating a 1 billionth submultiple of an SI unit ( ...

. VLPCs have been used extensively in the central tracking detector of the

D0 experiment D, or d, is the fourth letter in the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ''dee'' (pronounced ), plural ''dees''. History The ...

,D. Adams ''et al.'': "Performance of a Large Scale Scintillating Fiber Tracker Using VLPC Readout" ''IEEE Transactions on Nuclear Science'' 42(4) pp.401-406 (1995)D0 Collaboration: “The Upgraded D0 Detector” ''Nuclear Instruments and Methods'' A565 pp.463–537 (2006) and for muon beam-cooling studies for a muon collider ( MICE).M. Ellis ''et al.'', “The Design, Construction and Performance of the MICE Scintillating Fibre Trackers,” ''Nuclear Instruments and Methods'' A659 pp.136–153 (2011) They have also been evaluated for

quantum information science Quantum information science is an interdisciplinary field that seeks to understand the analysis, processing, and transmission of information using quantum mechanics principles. It combines the study of Information science with quantum effects in ...

.K. McKay "''Development of the Visible Light Photon Counter for Applications in Quantum Information Science''" Dissertation, Duke University, http://hdl.handle.net/10161/4990 (2011)

Notes

References

{{Reflist Photodetectors Quantum cryptography