How to Teleport Quantum Information

HOW TO TELEPORT QUANTUM INFORMATION OVER 100 KM of FIBER CREATING THE QUANTUM STATES The NIST experiment adds quantum information to a photon in its position in a very small slice of time. The photon can take a short path, or a long path, with a 50/50 chance . .. long short early late So it can be either "early" or "late" in the time bin. If we don't know which, then it's both-a quantum "superposition" in time. TIME Fone nanosecond- If the photon is in a super- position of two states, they can be in phase"- the peaks of their waves lining up with each other ... TIME OR "out of phase", with their waves cancelling each other out. TIME Simultaneous out-of-phase photons cancel out. THE EXPERIMENT 1. Generate a photon I. in superposition of possible states. A special crystal splits it into 2. two identical photons, a helper Generate an input pho- 3. ton in the state to be photon and an ouput photon. They are "entangled"- the state of one is duplicated in the state of the other. teleported. We pick its state: early, late or a superposition of both. output photon beam splitter The input photon and 4. the helper photon meet at a beam- splitter. Each has a 50/50 chance of going straight through or reflecting off at an angle. detector 1 detector 2 receiver A detector clicks when a 3. photon arrives. When one detector clicks early and the other clicks late, this means the helper and input photons are in opposite states: detector 3 detector 4 Because the output photon is O. entangled with the helper photon, we know it is in the same state-which is also (from Step 5) the opposite state of the input photon. In effect we've "teleported" the evil twin of the input photon. Detectors 3 and 4 measure the state of output photons to confirm. early vs. late OR in-phase vs. out-of-phase superposition Because of the photons' random paths, this happens at best only 25% of the time. The other 75% are discarded. EXAMPLE: Input Output early late CONTENT BY MARTIN STEVENS/NIST DESIGN BY KELLY IRVINE/NIST in-phase superposition out-of-phase superposition NIST National Institute of Standards and Technology U.S. Department of Commerce www.nist.gov INTENSITY "helper" photon 100 KM of optical fiber