The Quantum Handshake by John G. Cramer

Author:John G. Cramer
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

Now suppose that we arrange for the light source L to emit only one photon within a given time period. Then, if we do the measurement with no opaque object on path A, we should detect the photon at 100 % of the time. If we perform the same measurement with the opaque object Obj blocking path A, we should detect a photon at 25 % of the time, a photon at 25 % of the time, and should detect no photon at all 50 % of the time (because it was removed by Obj in path A). In other words, the detection of a photon at guarantees that an opaque object is blocking path A, although no photon had actually interacted with object Obj. This is the essence of the Elitzur and Vaidmann interaction-free measurement.

Note that if a photon is detected at detector , the issue of whether an object blocks path A is unresolved. However, in that case another photon can be sent into the system, and this can be repeated until either a photon is detected at or absorbed by Obj. The net result of such a recursive procedure is that 66 % of the time a photon will strike the object, resulting in no detection signal, while 33 % of the time a photon will be detected at , indicating without interaction that an object blocks the A path. Thus, the EV procedure has an efficiency for non-interactive detection of 33 %.

As before, in analyzing interaction-free measurements with the Transactional Interpretation, we will explicitly indicate offer waves by a specification of the path in a Dirac ket state vector , and we will underline the symbols for optical elements at which a reflection has occurred. Confirmation waves will similarly be indicated by a Dirac bra state vector , and will indicate the path considered by listing the elements in the time-reversed path with reflections underlined.

Fig. 6.16Offer waves a ---- and b ----

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.