Abstract
Quantum information protected by the topology of the storage medium is expected to exhibit long coherence times. Another feature is topologically protected gates generated through braiding of Majorana bound states (MBSs). However, braiding requires structures with branched topological segments which have inherent difficulties in the semiconductor–superconductor heterostructures now believed to host MBSs. In this paper, we construct quantum bits taking advantage of the topological protection and non-local properties of MBSs in a network of parallel wires, but without relying on braiding for quantum gates. The elementary unit is made from three topological wires, two wires coupled by a trivial superconductor and the third acting as an interference arm. Coulomb blockade of the combined wires spawns a fractionalized spin, non-locally addressable by quantum dots used for single-qubit readout, initialization, and manipulation. We describe how the same tools allow for measurement-based implementation of the Clifford gates, in total making the architecture universal. Proof-of-principle demonstration of topologically protected qubits using existing techniques is therefore within reach.
Highlights
Majorana bound states (MBSs) in topological superconductors (TSs) have been identified as promising candidates for topological carriers of quantum information [1,2,3,4]
This property is intimately connected to non-Abelian braiding of MBSs, meaning that readout results depend on the order in which MBSs are brought together and measured [1, 9,10,11,12]
The wire geometry is natural for interfacing the qubit with quantum dots (QDs), employed to read out and manipulate the stored quantum information
Summary
Since the Rabi frequency wz = e2 + ∣t0 + zt1∣2 depends on the qubit state z = 1, with carefully timed charge measurements, projective MBQ readout becomes possible, figure 2(c). The. Hadamard gate H = (x + z) 2 , effectively exchanging x- and z-eigenstates, follows by combined rotations H = Sz Sx Sz. In conclusion, we have described readout, initialization, manipulation, and entangling operations for MBQs, all of which can be tested in current state-of-the-art experiments. We have described readout, initialization, manipulation, and entangling operations for MBQs, all of which can be tested in current state-of-the-art experiments Using these tools, we devised a twoqubit universal quantum computer with protected Clifford gates.
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