Preparing highly entangled states: quantum phase transitions in spinor Bose-Einstein condensates and quantum neural networks


Speaker: Polina Feldmann
When: Mar. 9 2020 14:00
Where: Erwin Schrödinger Saal, Innsbruck

The first part of my talk will be devoted to the state preparation in spinor Bose-Einstein condensates. The ground state of a ferromagnetic spin-1 Bose-Einstein condensate undergoes two quantum phase transitions as a function of the effective quadratic Zeeman effect q. We have found that the ground state at q=0 is highly entangled, useful for quantum-enhanced interferometry, and allows for the heralded generation of macroscopic superposition states. The q=0 ground state can be prepared from a coherent state by adiabatically crossing a quantum phase transition. The desired quantum features are accessible under realistic conditions and for large particle numbers. In the second part of my talk I will discuss quantum neural networks (QNNs). Recently, a new kind of QNNs has been introduced. These QNNs are machine learning algorithms for processing quantum states on quantum computers. We have developed a method which employs such QNNs to efficiently denoise small highly entangled states, for example 4-qubit Greenberger-Horne-Zeilinger states. This method can be applied to any quantum states subject to any kind of noise. It relies exclusively on noisy target states. Our proposal is within the reach of current quantum devices.

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