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11 december 2018

Approved Industrial Partnership Programme

Number i26.
Title Topological quantum computation (TQC) 
Executive organisational unit BUW
Programme management Prof.dr.ir. L.P. Kouwenhoven
Duration 2011-2018
Cost estimate M€ 4.0
Partner(s) Microsoft

The realization of a quantum computer depends on the suppression of decoherence. Most qubit designs have ways to protect the information-carrying quantum state as much as possible but the protection is never complete. This makes the lifetime of a quantum superposition finite and qubit operations subject to errors. There is one exception to this inherent obstacle: topologically protected qubits; in short top-qubits. The intrinsic design of top-qubits is such that deformations do not change the qubit state. This intrinsic protection is the same as the protected winding-number of a belt with a single twist; deformations without breaking the belt cannot undo a single twist. It is obviously advantageous to build a complex quantum computer based on infinitely lived qubit states. Top-qubits have yet to be realized and currently exist only on paper in various theoretical proposals. Nevertheless, Microsoft Station Q has chosen to focus their qubit activities entirely on this approach. This IPP proposes to realize topologically-protected qubits in nanoscale solid state devices.

Background, relevance and implementation
Recent theoretical proposals have developed new schemes for top-qubits based on nano­devices with semiconductor nanowires and superconducting electrodes. It turns out that the leading proposals by Lutchyn et al. (2010) and Oreg et al. (2010) are based on previously realized devices (2006) by the Kouwenhoven group. The Kouwenhoven group thus has all the necessary expertise for upgrading their earlier devices into top-qubit devices. For this reason Microsoft Station Q intends to finance experimental research in Kouwenhoven's group.

This IPP aims at understanding and solving various scientific questions concerning the character of topological phases and states in condensed matter systems. The motivation of addressing these questions is the technological goal of a new form of computing, which is based on two new ingredients: quantum mechanics and topology. The realization of a full-scale quantum computer falls outside the timescale of this IPP. Within this programme we focus on the initial required steps: the realization and manipulation of top-qubits based on the development of solid state Majorana Fermions. Within the first tranche of this programme signatures of Majorana Fermions have been observed in 2012 (10.1126/science.1222360).

The final evaluation of this programme will consist of a self-evaluation initiated by the programme leader and is foreseen in 2018.

Please find a research highlight that was achieved in 2013 within this FOM programme here.