Topology is especially helpful here because many
global topological properties are, by definition, invariant under
deformation, and given that most errors are local, information encoded
in topological properties is robust against them. Unitary gates manipulate information stored in the “quantum
register”—a quantum system—and in this sense
ordinary (unitary) quantum evolution can be regarded as a computation. In order to read the result of this computation, however, the quantum
register must be measured. The measurement gate is a non-unitary gate
that “collapses” the quantum superposition in the register
onto one of its terms with a probability corresponding to its complex
coefficient. This, however,
doesn’t mean that measurements in different bases are equivalent
complexity-wise. Indeed, one of the difficulties in constructing
efficient quantum algorithms stems exactly from the fact that
measurement collapses the state, and some measurements are much more
complicated than others.
However, this work is the first time the erasure-error model has been applied to matter-based qubits. It follows a theoretical proposal last year from Thompson, Puri and Shimon Kolkowitz of the University of California-Berkeley. However, the main result of the study is not only the low error rates, but also a different way to characterize them without destroying the … Read More
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