3 research outputs found
Relational quantum computing using only maximally mixed initial qubit states
We disprove the conjecture of [1], namely that it would require smarter
authors to find a way of making the two-qubit singlet/triplet measurement
quantum computationally universal given an ensemble of initial single qubit
states with less than three linearly independent Bloch vectors. We show, in
fact, that an initial ensemble of maximally mixed single qubits suffices.Comment: 2 + epsilon page
A relational quantum computer using only two-qubit total spin measurement and an initial supply of highly mixed single qubit states
We prove that universal quantum computation is possible using only (i) the
physically natural measurement on two qubits which distinguishes the singlet
from the triplet subspace, and (ii) qubits prepared in almost any three
different (potentially highly mixed) states. In some sense this measurement is
a `more universal' dynamical element than a universal 2-qubit unitary gate,
since the latter must be supplemented by measurement. Because of the rotational
invariance of the measurement used, our scheme is robust to collective
decoherence in a manner very different to previous proposals - in effect it is
only ever sensitive to the relational properties of the qubits.Comment: TR apologises for yet again finding a coauthor with a ridiculous
middle name [12
Entanglement quantification and local discrimination
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