“Percolation, phase transitions, and topological quantum error correction”
Building a quantum computer is one of the central challenges in modern physics. One of the main obstacles to a practical realization is that existing approaches to quantum computation seem to be rather fragile to environmental noise and other imperfections. Only a small amount of noise can render a quantum computer completely useless.
In the first part of the talk I will review the two most promising approaches to overcoming the problem of noise in quantum computers: one which might be dubbed a `software’ approach, utilizing quantum error correcting codes, and a `hardware’ approach where physical robustness is built into the system, e.g. by making use of a new class of materials called topologically ordered systems.
Towards the end of the talk I will briefly describe some recent work on the effect of qubit loss robust quantum information processing schemes. Remarkably, we have found that robust quantum storage is possible even if up to half the qubits are lost, and furthermore fully fault tolerant quantum computation is possible if up to 24% of the qubits are lost. Both of these thresholds are related to percolation transitions. I briefly discuss the consequences for both software and hardware approaches to noise tolerance.
Speaker webpage: http://www3.imperial.ac.uk/people/sean.barrett