Abstract
We propose and analyze an all-magnetic scheme to perform a Young’s double slit experiment with a micron-sized superconducting sphere of mass amu. We show that its center of mass could be prepared in a spatial quantum superposition state with an extent of the order of half a micrometer. The scheme is based on magnetically levitating the sphere above a superconducting chip and letting it skate through a static magnetic potential landscape where it interacts for short intervals with quantum circuits. In this way, a protocol for fast quantum interferometry using quantum magnetomechanics is passively implemented. Such a table-top earth-based quantum experiment would operate in a parameter regime where gravitational energy scales become relevant. In particular, we show that the faint parameter-free gravitationally-induced decoherence collapse model, proposed by Diósi and Penrose, could be unambiguously falsified.
Highlights
Preparing a massive object in a spatial quantum superposition over distances comparable to its size is a tantalizing possibility
It would be intriguing to prepare large quantum superpositions of even larger masses such that one could enter into the gravitational quantum regime (GQR), which we define as follows
For a solid sphere of radius R and mass M, we define the timescale tG o 2Rh (GM2), where h is the Planck’s constant and G the Newton’s gravitational constant. tG has two interpretations: (i) it is the conjectured lifetime of a quantum superposition state of a single sphere delocalized over a distance R, according to the parameter-free [6, 7]3 gravitationally-induced decoherence collapse model proposed by Diósi and Penrose [8, 9], (ii) h tG is the kinetic energy of two spheres equivalent to the gravitational interaction energy of two point particles of the same mass separated by a distance 2R, a situation that could be used to measure G [10]
Summary
Preparing a massive object in a spatial quantum superposition over distances comparable to its size is a tantalizing possibility. We propose to attain spatially large quantum superpositions of masses 1013 amu, well inside the GQR, by abandoning the use of lasers and using instead an all-magnetic on-chip architecture This approach combines the following salient features: (i) cryogenic temperatures both for environment and the massive particle to minimize decoherence due to emission, scattering, and absorption of black-body radiation, (ii) the use of static magnetic potentials created by persistent currents to diamagnetically levitate the sphere [28] without creating decoherence (space environment is not required) as well as to exponentially speed-up quantum dynamics by using inverted potentials [29], and (iii) coupling the position of the sphere to quantum circuits on an integrated on-chip configuration to cool the center-of-mass motion to the ground state, to make a double-slit smaller than the size of the sphere by measuring the squared center-of-mass position [24], and to measure the interference pattern downstream.
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