Photo: Quantum minimum disturbance measurement setup at POSTECH

Available as a 800x1500 JPEG or a 1500x2900 JPEG (3.7 MiB)

Quantum minimum disturbance measurement setup at the Quantum optics and quantum information lab at POSTECH

Here is a quick description of what the thing does. 390 nm ultrafast laser pulses are focused into BBO crystal (on the foreground at the left) and produce 780 nm photon pairs at ±3.38° angle. Each photon of the pair is reflected off a mirror and collected into optical fiber (thick yellow cables). One photon triggers a single-photon detector (on the foreground at the right), the other photon passes through a polarization controller (not shown, to the left of the photo) and enters the quantum processing part of the setup (through a yellow cable in the background at the left). The rest of the setup (the entire background, left to right) does the following, in sequence: prepares a single-photon quantum state, measures it with an adjustable “strength” of measurement, and checks the output state after the measurement to determine how much it has been disturbed by the measurement. The four output fiber couplers (the rightmost things) are connected to four single-photon detectors (not shown on the photo). Read more about this experiment in So-Young Baek’s paper.

This picture illustrates Korean blog and is included in Picture Collection (ref. nr. minimum-disturbance-measurement-setup-20080418-3) on Photo Pages

Taken on April 18, 2008.
Nikon D40 digital camera, 18-55 lens at 52 mm, polarizer (minimizes reflections off the optical table), f/20 25sec, tripod, parts of the scene “light painted” with an incandescent torch during the exposure.

Vadim Makarov