2,102 research outputs found
Quantum-enhanced Secure Delegated Classical Computing
We present a quantumly-enhanced protocol to achieve unconditionally secure
delegated classical computation where the client and the server have both
limited classical and quantum computing capacity. We prove the same task cannot
be achieved using only classical protocols. This extends the work of Anders and
Browne on the computational power of correlations to a security setting.
Concretely, we present how a client with access to a non-universal classical
gate such as a parity gate could achieve unconditionally secure delegated
universal classical computation by exploiting minimal quantum gadgets. In
particular, unlike the universal blind quantum computing protocols, the
restriction of the task to classical computing removes the need for a full
universal quantum machine on the side of the server and makes these new
protocols readily implementable with the currently available quantum technology
in the lab
Silicon-based spin and charge quantum computation
Silicon-based quantum-computer architectures have attracted attention because
of their promise for scalability and their potential for synergetically
utilizing the available resources associated with the existing Si technology
infrastructure. Electronic and nuclear spins of shallow donors (e.g.
phosphorus) in Si are ideal candidates for qubits in such proposals due to the
relatively long spin coherence times. For these spin qubits, donor electron
charge manipulation by external gates is a key ingredient for control and
read-out of single-qubit operations, while shallow donor exchange gates are
frequently invoked to perform two-qubit operations. More recently, charge
qubits based on tunnel coupling in P substitutional molecular ions in Si
have also been proposed. We discuss the feasibility of the building blocks
involved in shallow donor quantum computation in silicon, taking into account
the peculiarities of silicon electronic structure, in particular the six
degenerate states at the conduction band edge. We show that quantum
interference among these states does not significantly affect operations
involving a single donor, but leads to fast oscillations in electron exchange
coupling and on tunnel-coupling strength when the donor pair relative position
is changed on a lattice-parameter scale. These studies illustrate the
considerable potential as well as the tremendous challenges posed by donor spin
and charge as candidates for qubits in silicon.Comment: Review paper (invited) - to appear in Annals of the Brazilian Academy
of Science
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