1. Conundrum1885

    Project "Schrödinger"

    Hi, is anyone interested in testing a little idea I had?

    I've now acquired some quantum sensors otherwise known as APDs, namely AD500-8 TO52S1 which avalanche at between 80 and 200V but for my purposes running them at 119V is better because the HV850 chips natively output +/-60V when running at a stable 4.2V

    My idea is essentially to test entanglement over a large distance, for this purpose I've designed a prototype EPE device (entangled photon emitter) consisting of nonlinear crystals and some other off-the-shelf components including superconductors and large area red Phlatlight(tm) LED which when cooled with LN2 should emit a stream of entangled photons to my two spatially separated detectors.

    According to the latest research in Nature the range of EP's in air is about 20km but obviously this depends on other factors such as atmospheric dust and water vapor.

    So a test over a mere 5km should work fine if everything else is set up properly, also can compensate for radioactive triggering of the APDs using an event masker based on GM tubes.

    Anyone interested?

  2. allthecoolshortnamesweretaken

    Interested, but pretty sure I'm > 5 km away.

    Good luck with the experiment, but do be be careful!

    1. Conundrum1885


      Can't believe someone downvoted me but hey.

      Did I do something wrong?

      Also even 15km *might* work at least for the RX end, the maximum angle is dependent on distance but last time I checked the photons are emitted at fractions of the Brewster angle.

      If I get it all working and the bearing and elevation are right you might get a couple of "hits" on a properly designed sensor and yes it is eye safe as the optical power is under 12W from the aperture with pulsing, the average power being just under Class 2 limits at 100 feet.

      This isn't a laser btw, the emitter is based on a projector lamp.

      1. Anonymous Coward
        Anonymous Coward

        Re: Thanks

        You were probably DV'd for specifying a range but not a start point. I'm totally up for some science; especially the kind that I can run from a pub; but statistically am probably am not within 5 -or indeed 15- km of you.

  3. Conundrum1885

    RE. Re. Thanks

    Guernsey to Herm might be doable, barely. On a cloudless night.

  4. allthecoolshortnamesweretaken

    Progress report?

  5. M7S

    No progress report because....

    ...clearly the cat's got his tongue

    1. Conundrum1885

      Re: No progress report because....

      I am trying to source some better emitters because even with a tailbiter circuit the diode is just too slow.

      The problem is that the large area of the emitter complicates things, this can be worked around by using IR rather than red (900nm) monolithic diodes and cooling those.

      Also its a better match to my diodes and lenses, hoping to use projector bits as these are readily available.

  6. Conundrum1885

    LD versus PLED

    Also worth trying: take the centre section from an old projection TV Fresnel lens and use this.

    Can cause problems so will need a physical shutter to protect the delicate diode in the event of excess light.

    For the APDs here a setup that may work is optocouplers to multiply the voltage (2*PP3) with lower noise and make the whole thing battery operated: data can be sent back to the analysis machine using Bluetooth.

    A row of burner diodes to create a ring of light rather than a single dot may well work and then each one can be independently driven so the pulses sum over distance but still keeping it below the Class 2 limits.

    1. Conundrum1885

      Re: LD versus PLED

      Hi, yes I did also find that part of the reason for non replication is that I forgot one critical issue.

      The diodes typically used in projectors have an antiparallel ESD diode, which itself causes all sorts of problems and can also prevent use as a precision sensor or solar cell.

      Its bond wire can be carefully (!) dissected or lasered out and then a 15K ceramic low inductance resistor placed across the now unprotected SLED to prevent it getting damaged and also to help discharge the very large (>500pF) internal capacitance.

      Also APDs are a pain in the neck to interface, requiring an instrumentation amplifier and other parts as well as a very precise voltage unique to each individual diode.

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