Blueprint for creating massive and large spatial quantum superposition in a lab

IQC Colloquium featuring Anupam Mazumdar, from the University of Groningen

We are led to create a massive and large spatial quantum superposition to probe the quantum nature of gravity in a laboratory. In particular, to witness the quantum entanglement mediated via the quantum nature of gravity, we will need to prepare a pure quantum state of mass 10^{-15} -10^{-14}Kg with a spatial quantum superposition of 10-100 microns and a coherence time of nearly 1-2 seconds. Achieving the ballpark of these numbers is incredibly challenging, and we will need to ensure that the initial state is as pure as it can be achieved, from the centre of mass cooling to the cooling of the bulk phonons. Levitating and releasing the diamond to create the spatial superposition in the vacuum exerted by the spin-dependent force requires an incredible, unprecedented level of control in the magnetic field.

I will provide the blueprint to create the quantum superposition with the help of the inhomogeneous magnetic field on a diamond-like crystal with an NV-centre. There are challenges to maintaining the coherence of the spin, maintaining the phonon vibrations, and the wobbling of the diamond. I will discuss how to protect the coherence from the butterfly to the hypothetical existence of Planet-X in our solar system. All these lead to incredible precision in controlling the current carrying wires in a chip. I will also discuss how to achieve these challenges in 5-10 years and propose another experiment to test the graviton's spin with a high-intensity laser beam in a cavity and a massive quantum system in a ground state. I will also discuss achieving the ground state of a massive 10 Kg object.

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