• Quantum sensors: Measuring even more pre

    From ScienceDaily@1:317/3 to All on Wed Mar 23 22:30:46 2022
    Quantum sensors: Measuring even more precisely

    Date:
    March 23, 2022
    Source:
    University of Innsbruck
    Summary:
    Two teams of physicists have designed the first programmable quantum
    sensor, and tested it in the laboratory. To do so they applied
    techniques from quantum information processing to a measurement
    problem. The innovative method promises quantum sensors whose
    precision reaches close to the limit set by the laws of nature.



    FULL STORY ========================================================================== Atomic clocks are the best sensors humankind has ever built. Today,
    they can be found in national standards institutes or satellites of
    navigation systems.

    Scientists all over the world are working to further optimize the
    precision of these clocks. Now, a research group led by Peter Zoller, a theorist from Innsbruck, Austria, has developed a new concept that can be
    used to operate sensors with even greater precision irrespective of which technical platform is used to make the sensor. "We answer the question of
    how precise a sensor can be with existing control capabilities, and give a recipe for how this can be achieved," explain Denis Vasilyev and Raphael Kaubru"gger from Peter Zoller's group at the Institute of Quantum Optics
    and Quantum Information at the Austrian Academy of Sciences in Innsbruck.


    ==========================================================================
    For this purpose, the physicists use a method from quantum information processing: variational quantum algorithms describe a circuit of quantum
    gates that depends on free parameters. Through optimization routines, the sensor autonomously finds the best settings for an optimal result. "We
    applied this technique to a problem from metrology -- the science of measurement," Vasilyev and Kaubru"gger explain. "This is exciting because historically advances in atomic physics were motivated by metrology,
    and in turn quantum information processing emerged from that. So, we've
    come full circle here," Peter Zoller enthuses. With the new approach, scientists can optimize quantum sensors to the point where they achieve
    the best possible precision technically permissible.

    Better measurements with little extra effort For some time, it has
    been understood that atomic clocks could run even more accurately by
    exploiting quantum mechanical entanglement. However, there has been a
    lack of methods to realize robust entanglement for such applications.

    The Innsbruck physicists are now using tailor-made entanglement
    that is precisely tuned to real-world requirements. With their
    method, they generate exactly the combination consisting of quantum
    state and measurements that is optimal for each individual quantum
    sensor. This allows the precision of the sensor to be brought close
    to the optimum possible according to the laws of nature, with only a
    slight increase in overhead. "In the development of quantum computers,
    we have learned to create tailored entangled states," says Christian
    Marciniak from the Department of Experimental Physics at the University
    of Innsbruck. "We are now using this knowledge to build better sensors." Demonstrating quantum advantage with sensors This theoretical concept
    was now implemented in practice for the first time at the University
    of Innsbruck, as the research group led by Thomas Monz and Rainer Blatt
    now reported in Nature. The physicists performed frequency measurements
    based on variational quantum calculations on their ion trap quantum
    computer. Because the interactions used in linear ion traps are still relatively easy to simulate on classical computers, the theory colleagues
    were able to check the necessary parameters on a supercomputer at the University of Innsbruck. Although the experimental setup is by no means perfect, the results agree surprisingly well with the theoretically
    predicted values. Since such simulations are not feasible for all sensors,
    the scientists demonstrated a second approach: They used methods to automatically optimize the parameters without prior knowledge. "Similar
    to machine learning, the programmable quantum computer finds its optimal
    mode autonomously as a high-precision sensor," says experimental physicist Thomas Feldker, describing the underlying mechanism.

    "Our concept makes it possible to demonstrate the advantage of quantum technologies over classical computers on a problem of practical
    relevance," emphasizes Peter Zoller. "We have demonstrated a crucial
    component of quantum- enhanced atomic clocks with our variational
    Ramsey interferometry. Running this in a dedicated atomic clock is
    the next step. What has so far only been shown for calculations of
    questionable practical relevance could now be demonstrated with a
    programmable quantum sensor in the near future -- quantum advantage."
    The research was financially supported by the Austrian Science Fund FWF,
    the Research Promotion Agency FFG, the European Union within the framework
    of the Quantum Flagship and the Federation of Austrian Industries Tyrol,
    among others.


    ========================================================================== Story Source: Materials provided by University_of_Innsbruck. Note:
    Content may be edited for style and length.


    ========================================================================== Journal References:
    1. Christian D. Marciniak, Thomas Feldker, Ivan Pogorelov, Raphael
    Kaubruegger, Denis V. Vasilyev, Rick van Bijnen, Philipp Schindler,
    Peter Zoller, Rainer Blatt, Thomas Monz. Optimal metrology with
    programmable quantum sensors. Nature, 2022; 603 (7902): 604 DOI:
    10.1038/s41586-022- 04435-4
    2. Raphael Kaubruegger, Denis V. Vasilyev, Marius Schulte, Klemens
    Hammerer,
    Peter Zoller. Quantum Variational Optimization of Ramsey
    Interferometry and Atomic Clocks. Physical Review X, 2021; 11 (4)
    DOI: 10.1103/ PhysRevX.11.041045 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/03/220323125115.htm

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