[QIP-Sem] QIP seminar, Mon 11/21, 4:00, 6C-442, Sergey Bravyi

[Peter Shor]

MIT Quantum Information Processing seminar
Monday 11/21 at 4:00 in 6C-442
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Sergey Bravyi (IBM Research)

Marginally self-correcting memory based on 3D topological qubits

Abstract:

A big open question in the quantum information theory concerns feasibility of a self-correcting quantum memory. A user of such memory would need quantum computing capability only to write and read  information. The storage itself requires no action from the user, as long as  the memory is put in contact with a cold enough thermal bath. In this talk I will prove that the 3D Cubic Code model discovered recently by Haah is a marginally self-correcting memory. For a fixed temperature T and sufficiently small lattices the memory time of the encoded qubit grows polynomially with the lattice size L. The degree of the polynomial is proportional to 1/T. The polynomial growth of the memory time holds only up to a certain critical value of L which is exponential in 1/T. The maximum memory time that can be achieved at a given temperature T is thus exponential in 1/T^2.  The main feature of the 3D Cubic Code Hamiltonian responsible for the self-correction is the energy landscape penalizin
 g any sequence of local errors resulting in a logical error. The energy barrier that must be overcome to implement a bit-flip or phase-flip on the encoded qubit grows as log(L).  This is a joint work with Jeongwan Haah (Caltech) Paper: PRL107, 150504 (2011) 

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