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Paper 1

Lattice Surgery with a Twist: Simplifying Clifford Gates of Surface Codes

Daniel Litinski, Felix von Oppen

Year
2017
Journal
arXiv preprint
DOI
arXiv:1709.02318
arXiv
1709.02318

We present a planar surface-code-based scheme for fault-tolerant quantum computation which eliminates the time overhead of single-qubit Clifford gates, and implements long-range multi-target CNOT gates with a time overhead that scales only logarithmically with the control-target separation. This is done by replacing hardware operations for single-qubit Clifford gates with a classical tracking protocol. Inter-qubit communication is added via a modified lattice surgery protocol that employs twist defects of the surface code. The long-range multi-target CNOT gates facilitate magic state distillation, which renders our scheme fault-tolerant and universal.

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Paper 2

Synthesis of Arbitrary Quantum Circuits to Topological Assembly: Systematic, Online and Compact

Alexandru Paler, Austin G. Fowler, Robert Wille

Year
2017
Journal
arXiv preprint
DOI
arXiv:1711.01387
arXiv
1711.01387

It is challenging to transform an arbitrary quantum circuit into a form protected by surface code quantum error correcting codes (a variant of topological quantum error correction), especially if the goal is to minimise overhead. One of the issues is the efficient placement of magic state distillation sub circuits, so-called distillation boxes, in the space-time volume that abstracts the computation's required resources. This work presents a general, systematic, online method for the synthesis of such circuits. Distillation box placement is controlled by so-called schedulers. The work introduces a greedy scheduler generating compact box placements. The implemented software, whose source code is available online, is used to illustrate and discuss synthesis examples. Synthesis and optimisation improvements are proposed.

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