Entangling unitary gates on distant qubits with ancilla feedback

Kerem Halil Shah, Daniel K. L. Oi

Research output: Working paper

Abstract

By using an ancilla qubit as a mediator, two distant qubits can undergo a non-local entangling unitary operation. This is desirable for when attempting to scale up or distribute quantum computation by combining fixed static local sets of qubits with ballistic mediators. Using a model driven by measurements on the ancilla, it is possible to generate a maximally entangling CZ gate while only having access to a less entangling gate between the pair qubits and the ancilla. However this results in a stochastic process of generating control phase rotation gates where the expected time for success does not correlate with the entangling power of the connection gate. We explore how one can use feedback into the preparation and measurement parameters of the ancilla to speed up the expected time to generate a CZ gate between a pair of separated qubits and to leverage stronger coupling strengths for faster times. Surprisingly, by choosing an appropriate strategy, control of a binary discrete parameter achieves comparable speed up to full continuous control of all degrees of freedom of the ancilla.
LanguageEnglish
Number of pages8
Publication statusPublished - 14 Nov 2013

Fingerprint

phase control
stochastic processes
quantum computation
ballistics
degrees of freedom
preparation

Keywords

  • ancilla qubit
  • entangling unitary operation
  • coupling strength

Cite this

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Entangling unitary gates on distant qubits with ancilla feedback. / Halil Shah, Kerem; K. L. Oi, Daniel.

2013.

Research output: Working paper

TY - UNPB

T1 - Entangling unitary gates on distant qubits with ancilla feedback

AU - Halil Shah, Kerem

AU - K. L. Oi, Daniel

PY - 2013/11/14

Y1 - 2013/11/14

N2 - By using an ancilla qubit as a mediator, two distant qubits can undergo a non-local entangling unitary operation. This is desirable for when attempting to scale up or distribute quantum computation by combining fixed static local sets of qubits with ballistic mediators. Using a model driven by measurements on the ancilla, it is possible to generate a maximally entangling CZ gate while only having access to a less entangling gate between the pair qubits and the ancilla. However this results in a stochastic process of generating control phase rotation gates where the expected time for success does not correlate with the entangling power of the connection gate. We explore how one can use feedback into the preparation and measurement parameters of the ancilla to speed up the expected time to generate a CZ gate between a pair of separated qubits and to leverage stronger coupling strengths for faster times. Surprisingly, by choosing an appropriate strategy, control of a binary discrete parameter achieves comparable speed up to full continuous control of all degrees of freedom of the ancilla.

AB - By using an ancilla qubit as a mediator, two distant qubits can undergo a non-local entangling unitary operation. This is desirable for when attempting to scale up or distribute quantum computation by combining fixed static local sets of qubits with ballistic mediators. Using a model driven by measurements on the ancilla, it is possible to generate a maximally entangling CZ gate while only having access to a less entangling gate between the pair qubits and the ancilla. However this results in a stochastic process of generating control phase rotation gates where the expected time for success does not correlate with the entangling power of the connection gate. We explore how one can use feedback into the preparation and measurement parameters of the ancilla to speed up the expected time to generate a CZ gate between a pair of separated qubits and to leverage stronger coupling strengths for faster times. Surprisingly, by choosing an appropriate strategy, control of a binary discrete parameter achieves comparable speed up to full continuous control of all degrees of freedom of the ancilla.

KW - ancilla qubit

KW - entangling unitary operation

KW - coupling strength

UR - http://arxiv.org/abs/1311.3463

M3 - Working paper

BT - Entangling unitary gates on distant qubits with ancilla feedback

ER -