Quantum heat pump: a new measuring tool for physicists

  • Quantum heat pump: a new measuring tool for physicists Physicists have built a quantum scale heat pump made from particles of light (photons). This device brings scientists closer to the quantum limit of measuring radio frequency signals, useful in for example the hunt for dark matter.

    The device, known as a photon pressure circuit, is made from superconducting inductors and capacitors on a silicon chip cooled to only a few millidegrees above absolute zero temperature. While this sounds very cold, for some of photons in the circuit, this temperature is very hot, and they are excited with thermal energy. Using photon pressure, the researchers can couple these excited photons to higher frequency cold photons, which in previous experiments allowed them to cool the hot photons into their quantum ground state.

    In this new work, the authors add a new twist: by sending an extra signal into the cold circuit, they are able to create a motor which amplifies the cold photons and heats them up. At the same time, the extra signal “pumps” the photons preferentially in one direction between the two circuits. By pushing photons harder in one direction than the other, the researchers are able to cool the photons in one part of the circuit to a temperature that is colder than the other part, creating a quantum version of the heat pump for photons in a superconducting circuit.

    An illustration of the device , which consists of two superconducting circuits: a cold high frequency circuit (in blue) and a hot low frequency circuit (in red).


    Here, the current that flows in the red circuit generates an oscillating magnetic field which leads to the photon-pressure coupling. By sending in a strong signal to the blue high-frequency circuit, this one is transformed into an amplifier capable of detecting radio-frequency photons flowing in the red circuit with much higher sensitivity.

    Note that overunity Tesla coils work in similar way - they just require to achieve high-enough voltage between neighbouring loops of their windings for to constrain electron motion there in similar way, like within superconductors. The dark matter detectors thus increasingly look like many empirically built overunity circuits. The self-amplifying principle of stochastic resonance comes on mind here. Stochastic resonance (SR) is a phenomenon where a signal that is normally too weak to be detected by a sensor, can be boosted by adding white noise to the signal, which contains a wide spectrum of frequencies. An overdamped particle in a periodically oscillating double-well potential is subjected to Gaussian white noise, which induces transitions between the potential wells. We again have cyclic process which has activation barrier assisted by random noise. Further, the added white noise can be filtered out of signal to effectively detect the original, previously undetectable signal.


    This phenomenon extends to many other systems - whether electromagnetic, physical or biological - and is an area of intense research. In general the phenomena with time-arrow reversed can be promoted by periodic signal, which is for example reason why oversaturated solutions of gas or crystals can be thermalized by shaking or why low-frequency light quenches the photoluminiscence. In this sense it helps to imagine that dark matter particles can be perceived like bubbles of vacuum in terms of their negative space-time curvature. Their detectors just runs in time-reversed way than normal antennae: we introduce weak periodic signal to it and we get anharmonic impulses in reward. It's good to note that topological insulators like graphene (which is able to gain energy from motion of its layers), bucking ferromagnets and/or capacitors charged to a high voltage share many aspects with superconductor circuits at low temperatures in terms of geometric frustration of charge carriers motion. See also:

  • In large scale of things, the energy processes aren't always reversible - the energy gets sometimes accumulated in processes, which required high activation barrier for their transition. This is how uranium reserves actually work: we are actually using fossil energy frozen during supernova explosions, when heavy elements have been also formed, but the system was cooled way too fast for to decay back again.

    The AdS/CFT theorem indicates, that most of high energy phenomena should also have their counterpart at low energy density scales, so that dark matter is stuff of the same nature: an space-time bubbles (mirror matter) which just wait for their popping and release of excess of energy. Except that with compare to atom nuclei the energy density and activation energy barrier for it is much lower. But this fossil energy may be still quite significant, because with compare to uranium dark matter particles are way more widespread and abundant.