It is not very difficult to generate signals with one photon on average, but, it is quite difficult to generate exactly one photon each time. To encode quantum information on photons, you want there to be exactly one, according to postdoctoral associates Andrew Houck and David Schuster who are lead co-authors on the first paper.
We are reporting the first such source for producing discrete microwave photons, and the first source to generate and guide photons entirely within an electrical circuit, said Schoelkopf.
In order to successfully perform these experiments, the researchers had to control electrical signals corresponding to one single photon. In comparison, a cell phone emits about 1023 (100,000,000,000,000,000,000,000) photons per second. Further, the extremely low energy of microwave photons mandates the use of highly sensitive detectors and experiment temperatures just above absolute zero.
In this work we demonstrate only the first half of quantum communication on a chip quantum information efficiently transferred from a stationary quantum bit to a photon or flying qubit, says Schoelkopf. However, for on-chip quantum communication to become a reality, we need to be able to transfer information from the photon back to a qubit.
This is exactly what the researchers go on to report in the second breakthrough. Postdoctoral associate Johannes Majer and graduate student Jerry Chow, lead co-authors of the second paper, added a second qubit and used the photon to transfer a quantum state from one qubit to another. This was possible because the microwave photon could be guided on wires similarly to the way fiber optics can guide visible light and c
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