Figure 1
In the figure,
stands for the light source,
is the optical circulator,
,
,
, and
are photon detectors, PBS stands for polarizing beam splitter, which only reflects vertically polarized photons (
), SPR stands for switchable polarization rotator, PC stands for Pockels cell that determines the polarization state of the transmitted photons, SM stands for switchable mirror, MR stands for a normal mirror, and OD stands for optical delay. Only horizontally polarized photons (
) will be sent into the tandem Michelson interferometers. The two optical paths
and
for the first Michelson interferometer correspond to the outer cycle of the chained quantum Zeno effect CQZE (
cycles) in Mach-Zehnder setup, while the paths
and
for the second Michelson interferometer, correspond to the inner cycle of the CQZE (
cycles). The mirror
is switched off initially to allow the photon to be transmitted but it then remains on for
cycles, and is turned off again after
cycles are completed. Here
rotates the polarization by a small angle
(for each cycle, the photon passes SPR twice), i.e.,
evolves to
and
evolves to
.
and
guarantee that optical distances of different paths of same interferometer exactly match. At Bob’s end, Bob passes an
photon by turning off his PC reflecting it back, and he blocks an
photon by turning on his PC, changing the photon’s polarization to
. We emphasize that the chance of Alice’s photon leaking into the transmission channel is virtually zero for large enough
and
.
Reuse & Permissions