Conditional Phase Gate for Photonic Qubits


Technology # 19-09



We present a design for a quantum logical gate between single photons (specifically, a conditional phase gate) with the following properties:


* It is deterministic in principle (photon losses would make it probabilistic, but the failure probability can be reduced exponentially fast by adopting a redundant strategy).

* It is completely passive, requiring no external fields to manipulate the device at any stage (no energy consumption).

* It does not rely on or require the assistance of quantum memories or any kind of nonlinear optical device.

* It has no moving parts; it could be built on a chip using already existing solid-state technology.

* It acts on “flying photons” (does not require storage and retrieval): the photons would just pass through the device flying in opposite directions and acquire a 1/2 phase shift whenever both of them are present (relative to the case where only one of them is).




A conditional phase gate between photons can be used to, essentially, build a single-photon photonic transistor, which could be used for single-photon switches and routers.  It can also be used to carry out a complete, deterministic Bell-state measurement on a photon pair.  This has applications to the deterministic generation of entangled states, with potential uses in quantum cryptography and to build quantum repeaters; devices relying on quantum teleportation; and, of course, quantum computers.




* Photons are excellent carriers of quantum information, requiring only optical fibers to travel, and single-photon logical operations are trivial, which is why photons have the field to themselves in, for instance, quantum cryptography applications.  Our invention would add substantially to these already well-known advantages, by essentially removing the photons’ only weakness. 

* The ability to engineer logical gates between photons would make it possible, for instance, to build efficient quantum repeaters, thereby greatly extending the range of existing quantum communication networks.  Individual photons are also cheap to produce and carry very little energy, so a photonic quantum computer consisting entirely of passive gates could run at extremely high clock speeds and require very little power to operate. 




A design for a quantum logical gate between single photons (specifically, a conditional phase gate) with the following properties



This invention/technology is available for licensing.

For interested parties seeking further information, feel free to contact:

Mark Allen Lanoue

Technology Manager / Tech Ventures

University of Arkansas

(479) 575-7243




Patent Information:
For Information, Contact:
Mark Lanoue
Technology Manager
University of Arkansas
Julio Gea-Banacloche
William Konyk
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