QLunch: Preparation and Compression of Symmetric Pure Quantum States

Speaker: Andreas Baertschi, Los Alamos National Laboratory   

Title: Preparation and Compression of Symmetric Pure Quantum States

Abstract: In this talk I will present a deterministic scheme for the preparation of symmetric pure n-qubit quantum states (symmetric under permutation of the qubits). Implemented as a circuit, our scheme has linear depth, needs no ancilla qubits and -- used in reverse -- yields a  quasilinear-depth circuit for efficient compression of symmetric pure states into logarithmically many qubits.

The scheme relies on an inductive approach to prepare. Dicke states |Dnk⟩, which form an orthonormal basis of the subspace of symmetric pure n-qubit states. We prepare these states, which are equal superpositions of all n-qubit states with Hamming Weight k, using O(nk) gates in O(n) depth. All properties also hold for Linear Nearest Neighbor architectures.

Talk based on joint work with Stephan Eidenbenz, "Deterministic Preparation of Dicke States", FCT 2019, arXiv:1904.07358.

Andreas Baertschi has been working as a CNLS Postdoc at Los Alamos National Laboratory since October 2018. His research interests lie in Theoretical Computer Science and in Quantum Computing. Prior to LANL Andreas was a Postdoc at ETH Zurich, Switzerland. He holds a PhD in Computer Science and a MSc in Mathematics.