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A Experiments probing the macroscopic limits of QM

  1. Feb 13, 2017 #1
    This thread is to serve as both a compilation and ground of discussion of key experiments, both historical and planned, which attempt to probe possible macroscopic limits of QM, taking into account e.g. some particular gravitational/optical/mechanical/superconducting/etc aspect and/or phenomenon.

    I will start by posting a few known and perhaps some not so well known ones:

    Colella et al. 1975, Observation of Gravitationally Induced Quantum Interference
    Marshall et al. 2002, Towards quantum superpositions of a mirror
    Vanner et al. 2013, Cooling-by-measurement and mechanical state tomography via pulsed optomechanics
    Kiesel et al. 2013, Cavity cooling of an optically levitated submicron particle
    Kaltenbaek et al. 2015, Macroscopic quantum resonators (MAQRO): 2015 Update
    Last edited by a moderator: May 8, 2017
  2. jcsd
  3. Feb 20, 2017 #2
    Thanks for the thread! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post? The more details the better.
  4. Feb 21, 2017 #3
    The Marshall et al experiment to demonstrate macroscopic quantum superposition of a mirror was apparently proposed in 2002. Any idea whether it was ever actually attempted?
  5. Feb 21, 2017 #4
    There has indeed been a significant amount of work towards realizing the Marshall et al. experiment since then. There are many groups around the world actively pursuing this experiment and variations thereof.

    Perhaps the best known one is by one of the authors of Marshall et al., the UCSB/Leiden experimentalist Dirk Bouwmeester. Incidentally, he was also involved (first author) in the original quantum teleportation experiments in Anton Zeilinger's group back in '97. Moreover, Bouwmeester recently, in 2014, got the Spinoza Prize, effectively a 2.5 million euro grant from the NWO, to help fund this particular Marshall et al. experiment.

    Here is an hour long lecture of his on the state of the experiment in 2013:

    Here are some of the more recent (2008 to 2016) key publications by members of Bouwmeester's experimental group on arxiv w.r.t. this experiment:

    Kleckner et al. 2008, Creating and Verifying a Quantum Superposition in a Micro-optomechanical System
    Pepper et al. 2011, Optomechanical superpositions via nested interferometry
    Pepper et al. 2012, Macroscopic superpositions via nested interferometry: finite temperature and decoherence considerations
    Ghobadi et al. 2014, Opto-mechanical micro-macro entanglement
    Weaver et al. 2015, Nested Trampoline Resonators for Optomechanics
    Buters et al. 2016, Optomechanics with a polarization non-degenerate cavity
  6. Feb 21, 2017 #5
    Here are some more key articles, including a 2014 review of the Marshall et al. experiment. They all seem to be behind pay walls though:

    Kleckner et al. 2011, Optomechanical trampoline resonators
    Pepper et al. 2014, Towards Macroscopic Superpositions via Single-photon Optomechanics
    Eerkens et al. 2015, Optical side-band cooling of a low frequency optomechanical system
  7. Feb 24, 2017 #6
  8. Apr 15, 2017 #7
    MAGA gravitational wave detector based on phonon excitations in BECs:

    Sabin et al. 2014, Phonon creation by gravitational waves
    Followup paper:

    Sabin et al. 2016, Thermal noise in BEC-phononic gravitational wave detectors
    Review article by the same group about gravity in quantum experiments:
    Howl et al. 2016, Gravity in the Quantum Lab
  9. Apr 16, 2017 #8


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    In other words: "We have no idea how to build it now, but it is not 10 orders of magnitude away."
    Or, in this case: "We achieved the necessary temperature, the necessary number of atoms in the BEC, and the necessary lifetime individually, but achieving them at the same time will be very challenging - oh, and we have to put all this into some vibration-free environment, and we need this 1 million times or need a source that emits gravitational waves long enough for 1 million measurements".

    An interesting approach, but I don't see this happening for quite some time.

    Edit: Now discussed here
    Last edited: Apr 16, 2017
  10. Apr 18, 2017 #9

    Large Quantum Superpositions and Interference of Massive Nanometer-Sized Objects


    We propose a method to prepare and verify spatial quantum superpositions of a nanometer-sized object separated by distances of the order of its size. This method provides unprecedented bounds for objective collapse models of the wave function by merging techniques and insights from cavity quantum optomechanics and matter-wave interferometry. An analysis and simulation of the experiment is performed taking into account standard sources of decoherence. We provide an operational parameter regime using present-day and planned technology.

    Quantum interference of large organic molecules


    The wave nature of matter is a key ingredient of quantum physics and yet it defies our classical intuition. First proposed by Louis de Broglie a century ago, it has since been confirmed with a variety of particles from electrons up to molecules. Here we demonstrate new high-contrast quantum experiments with large and massive tailor-made organic molecules in a near-field interferometer. Our experiments prove the quantum wave nature and delocalization of compounds composed of up to 430 atoms, with a maximal size of up to 60Å, masses up to m=6,910AMU and de Broglie wavelengths down to λdB=h/mv1pm. We show that even complex systems, with more than 1,000 internal degrees of freedom, can be prepared in quantum states that are sufficiently well isolated from their environment to avoid decoherence and to show almost perfect coherence.

    A strict experimental test of macroscopic realism in a superconducting flux qubit


    Macroscopic realism is the name for a class of modifications to quantum theory that allow macroscopic objects to be described in a measurement-independent manner, while largely preserving a fully quantum mechanical description of the microscopic world. Objective collapse theories are examples which aim to solve the quantum measurement problem through modified dynamical laws. Whether such theories describe nature, however, is not known. Here we describe and implement an experimental protocol capable of constraining theories of this class, that is more noise tolerant and conceptually transparent than the original Leggett–Garg test. We implement the protocol in a superconducting flux qubit, and rule out (by ∼84 s.d.) those theories which would deny coherent superpositions of 170 nA currents over a ∼10 ns timescale. Further, we address the ‘clumsiness loophole’ by determining classical disturbance with control experiments. Our results constitute strong evidence for the superposition of states of nontrivial macroscopic distinctness.

    Experiments testing macroscopic quantum superpositions must be slow


    We consider a thought experiment where the preparation of a macroscopically massive or charged particle in a quantum superposition and the associated dynamics of a distant test particle apparently allow for superluminal communication. We give a solution to the paradox which is based on the following fundamental principle: any local experiment, discriminating a coherent superposition from an incoherent statistical mixture, necessarily requires a minimum time proportional to the mass (or charge) of the system. For a charged particle, we consider two examples of such experiments, and show that they are both consistent with the previous limitation. In the first, the measurement requires to accelerate the charge, that can entangle with the emitted photons. In the second, the limitation can be ascribed to the quantum vacuum fluctuations of the electromagnetic field. On the other hand, when applied to massive particles our result provides an indirect evidence for the existence of gravitational vacuum fluctuations and for the possibility of entangling a particle with quantum gravitational radiation.
    Last edited: Apr 18, 2017
  11. Apr 24, 2017 #10
    Gerlich et al. 2011, Quantum interference of large organic molecules
    Emary et al. 2013, Leggett-Garg Inequalities
    Lychkovskiy 2015, Large quantum superpositions of a nanoparticle immersed in superfluid helium
    Hu et al. 2016, Strictly nonclassical behavior of a mesoscopic system
    Naeij et al. 2016, Double-Slit Interference Pattern for a Macroscopic Quantum System
    Yin et al. 2016, Bringing quantum mechanics to life: from Schrödinger's cat to Schrödinger's microbe
  12. May 1, 2017 #11
    Fray et al. 2004, Atomic Interferometer with Amplitude Gratings of Light and its Applications to Atom Based Tests of the Equivalence Principle
    Touboul et al. 2012, The MICROSCOPE experiment, ready for the in-orbit test of the equivalence principle
    Schlippert et al. 2014, Quantum Test of the Universality of Free Fall
    Altschul et al. 2014, Quantum Tests of the Einstein Equivalence Principle with the STE-QUEST Space Mission
    Will 2014, The Confrontation between General Relativity and Experiment
    Zych et al. 2015, Quantum formulation of the Einstein Equivalence Principle
    Orlando et al. 2016, A test of the equivalence principle(s) for quantum superpositions
    Rosi et al. 2017, Quantum test of the equivalence principle for atoms in superpositions of internal energy eigenstates
    Last edited: May 1, 2017
  13. May 1, 2017 #12
    Thanks for sources, not thanks for destroying my free time.
  14. Aug 13, 2017 #13
    Bialynicki-Birula et al. 1976, Nonlinear wave mechanics
    Gähler et al. 1981, Neutron optical tests of nonlinear wave mechanics
    Bassi et al. 2013, Models of wave-function collapse, underlying theories, and experimental tests.
    Curceanu et al. 2015, X-rays help to unfuzzy the concept of measurement
    Arndt et al. 2014, Testing the limits of quantum mechanical superpositions.
    Cotter et al. 2017, In search of multipath interference using large molecules
  15. Dec 11, 2017 #14
    Koduru Joshi et al. 2017, Space QUEST mission proposal: Experimentally testing decoherence due to gravity
    Rätzel et al. 2017, Testing small scale gravitational wave detectors with dynamical mass distributions
    Rätzel et al. 2017, Frequency spectrum of an optical resonator in a curved spacetime
    Hartley et al. 2017, Analogue simulation of gravitational waves in a 3+1 dimensional Bose-Einstein condensate
  16. Jan 17, 2018 #15
  17. Jan 17, 2018 #16
    Interesting experiment.

    Probably what we (humain being) perceive is not what is in itself.

    For example we perceive this chair of green colors which leads us to say that this chair is green. Which leads us to think that color (first-person experience) is an intrinsic property of light.


    However, there is another interpretation.


    Tommy Edison, who has been blind since birth, talks about describing colors to blind people.
    it seems to me, therefore, that in order to build a rational understanding of macroscopic / microscopic interaction, all the factors must be taken into account, belonging to the different scientific fields.

    Experiments to transmit quantum information using satellite already exist : https://arxiv.org/pdf/1712.09722.pdf

    Best regards
    Last edited: Jan 18, 2018
  18. Jan 18, 2018 #17


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  19. Jan 18, 2018 #18
    The phys.org article is a copypaste from the university's website, unfortunately neither of them link to a paper. It of course goes without saying that these news outlets specifically post clickbait articles to garner more interest and generate hype. It is very clear that the goal of the experiment is of purely scientific interest and that all the mentioned potential spinoffs and technologies are afterthoughts used to justify the experiment to the public; its understandable but still somewhat a shame that stating such justifications for science are today part of academic guidelines when writing a paper, but hey, in a capitalist society fundamental science funding just isn't cheap.

    I have not found any actual papers yet regarding the proposed experiment, a quick search of the papers of one of the researchers involved (Mauro Paternostro) reveals nothing about Project TEQ, but it does show he is involved in the MAQRO experiment proposal I linked to earlier in this thread. I'm pretty confident that he knows the distinction between environmental and intrinsic decoherence, seeing there are multiple review articles on the subject.
  20. Jan 18, 2018 #19


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    More information on Project TEQ can be found at http://cordis.europa.eu/project/rcn/211916_en.html
  21. Jan 18, 2018 #20
    Thanks. This is very exciting stuff. Does the reported timetable there (until 12/31/2021) refer to funding time or to projected time until the measurements are finished, before data analysis is done?

    I'm asking because to me a mere four years seems like a ridiculously short time to finish an experiment of this magnitude, at least in comparison with the ongoing efforts of groups carrying out the Marshall et al. experiment. If TEQ is just 5 years away from having significant results, this may actually be finished before Bouwmeester's decades long ongoing attempt.

    It would definitely be nice though, especially seeing it may just fall within Penrose's lifespan, who is of course the theorist whose ideas and work have resulted in most of these experiments looking for deviations from QM for ≥ Planck mass systems in superposition.
  22. Jan 19, 2018 #21


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    It is the funding time; they have to finish all their activities by then and then submit their final report within a few months (I think it is 6 months) after this date.
    Note that there is nothing that says that they will actually finish by then; most of the time you get funding for three or four years and if you have an experiment that takes longer than that to complete you just have to fund it from two (or more) separate projects. They might also have some funding from elsewhere (not for the same activities but for e.g. salaries for scientist working on the projects) and can of course use existing facilities/ setups for the work . This is not the kind of work someone would start from scratch and expect to complete in 4 years.

    The projects should have a website up and running soon (it is a requirement for this type of project, part of the mandatory "impact" workpackage)
    Last edited: Jan 19, 2018
  23. Apr 25, 2018 #22

    "In work recently published in Nature, a team led by Prof. Mika Sillanpää at Aalto University in Finland has shown that entanglement of massive objects can be generated and detected.

    The researchers managed to bring the motions of two individual vibrating drumheads—fabricated from metallic aluminium on a silicon chip—into an entangled quantum state. The macroscopic objects in the experiment are truly massive compared to the atomic scale—the circular drumheads have a diametre similar to the width of a thin human hair."
  24. Apr 25, 2018 #23


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    It is interesting to get two entangled macroscopic waves. The publication is available here
    ( I think it is the same one. Same subject matter )
  25. May 18, 2018 #24
    An addition:



    From the phys.org article:
  26. Jun 11, 2018 #25

    ...I would have preferred a somewhat "larger" object

    Nonclassicality of the Harmonic-Oscillator Coherent State Persisting up to the Macroscopic Domain


    Can the most “classical-like” of all quantum states, namely the Schrödinger coherent state of a harmonic oscillator, exhibit nonclassical behavior? We find that for an oscillating object initially in a coherent state, merely by observing at various instants which spatial region the object is in, the Leggett-Garg inequality (LGI) can be violated through a genuine negative result measurement, thereby repudiating the everyday notion of macrorealism. This violation thus reveals an unnoticed nonclassicality of the very state which epitomizes classicality within the quantum description. It is found that for any given mass and oscillator frequency, a significant quantum violation of LGI can be obtained by suitably choosing the initial peak momentum of the coherent state wave packet. It thus opens up potentially the simplest way (without coupling with any ancillary quantum system or using nonlinearity) for testing whether various recently engineered and sought after macroscopic oscillators, such as feedback cooled thermal trapped nanocrystals of ∼106–109  amu mass, are indeed bona fide nonclassical objects.


    Last edited by a moderator: Jun 11, 2018
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