Shanni presented on “Construction of an Entangled Photon Source for Experimenting with Quantum Technologies” at the 2015 Hackaday SuperConference.
Her lecture has been uploaded by Hackaday and is available now available online. CLICK HERE for the link to the HaD Blog and Video.
A recent paper entitled “Displacing entanglement back and forth between the micro and macro domains” discusses the experimental possibility of displacing quantum entanglement into the domain where it involves two macroscopically distinct states, i.e. two states characterized by a large enough number of photons. Specifically, the authors describe the process by which they start with two entangled spatially separated optical modes at the single photon level and subsequently displace one of these modes up to almost a thousand photons.
With so many photons, it would be possible, at least in principle, to see entangled photon pulses with our eyes. This would also make it possible to perform entanglement experiments with linear coarse-grain detectors (NOT single-photon detectors).
Mathieu Stephan, a high speed electronics engineer at the Swiss quantum information systems company id Quantique SA (and prolific hardware hacker) designed the very fast pulse amplifiers needed to acquire signals from avalanche photodiodes for this experiment. He has posted a thorough description of his design on his blog: http://www.limpkin.fr.
Today I found two Perkin Elmer SPCM-AQE-13-FC SPCMs for sale on eBay at $400 each. eBay auction numbers are 280877451350 and 280877453169. I am passing along this information in case that blog readers may be interested. I have no connection whatsoever to seller.
Someone (I don’t know the seller) is selling brand new Perkin Elmer C30902E Silicon Avalanche Photodiodes on eBay. Auction number: 200747161278.
These are NOT chilled by a thermoelectric cooler, so their internal noise may be too large for experiments with entangled photons unless you rig some sort of external Peltier element to keep them chilled. However, if you are developing a SPCM, using $91 SPADs during debugging is a lot better than frying $1,000 TE-cooled SPADs.
I. Rech, I. Labanca, M. Ghioni, and S. Cova of the Politecnico di Milano in Italy described an interesting modification to the Perkin Elmer SPCM-AQR Single-Photon Counting Module (SPCM) to improve its timing characteristics in:
I. Rech, I. Labanca, M. Ghioni, and S. Cova, “Modified single photon counting modules for optimal timing performance“, Rev. Sci. Instrum. 77, 033104 (2006); doi:10.1063/1.2183299 (5 pages). Continue reading
Image Credit: Excelitas Technologies
Figure 144 in the book shows the schematic diagram for our d.i.y. passively-quenched SPCM based on a Perkin-Elmer C30902S-DTC SPAD.
In our circuit, the SPAD is reverse-biased through a 200kΩ resistor. This value is sufficiently large that an avalanche in the SPAD will be quenched by itself within less than a nanosecond. The pulses produced by the SPAD are AC-coupled to a fast constant-level discriminator which has an output that is compatible with TTL logic circuits. Continue reading
Our diy entangled-photon source, shown in the book’s Figure 142, uses two BBO crystals that support type I down-conversion that are mounted according to a design by Paul Kwiat and his colleagues at the Los Alamos National Laboratory.
The nonlinear crystal in our photon entangler comprises two 5 mm x 5 mm x 0.1 mm BBO crystals mounted face-to-face at an angle of 90 degrees to each other. As shown in the book’s Figure 140, pump photons polarized at 45 degrees produce two cones of entangled down-converted photons.
This is the 405 nm pump laser used in the circuit shown in the book’s Figure 141. The laser is built from a Blu Ray disk burner laser diode. We drive the laser diode with 160 mA to produce around 100 mW of 405-nm polarized light. The laser diode is capable of producing 250 mW, but we prefer to drive it much more conservatively. Continue reading
This picture supplements Figure 148 in the book. The colors should help you visualize the paths of the beams in our entangled-photon source: Violet – 405 nm pump laser beam; Pink – 810 nm signal and idler entangled-photon beams. A detailed schematic diagram for the entangler is available in the book’s Figure 147. Figure 149 shows the 405 nm beamstop. Continue reading
quTools of München, Germany is the maker of the quED quantum entangled state demonstrator system to generate and analyze polarization entangled photons. This system is a professionally-manufactured version of the type of entangled-photon generator used by many universities, and similar to the diy version described in Chapter 8 of our book (Figure 148).
quED employs a spontaneous parametric down conversion process (type I or type II; collinear or non-collinear) to generate polarization entangled photon pairs. Fiber-coupled single photon detectors in connection with polarizing filters are used to detect the photon pairs, analyze their polarizations and verify their non-classical correlations. Continue reading
ALPhA (Advanced Laboratory Physics Association) has worked out a deal with Excelitas to sell Single-Photon Counting Modules (SPCMs) to instructional labs. The detectors carry labels specifying that these units belong in the undergraduate instructional labs and not in research labs. These educational detectors have reduced specs, notably a higher background dark count rate, compared to other models from the company.
The set of four SPCMs can be purchased for $5,720 (instead of the usual ~$10k). Continue reading
This is an inside view of the two-channel photon and coincidence counter of the book‘s Figure 145. It is used in the photon entanglement experiments of Chapter 8. Continue reading
