Oxford University Innovation Ltd

Quantum Motion Technologies Limited

Simon Benjamin

Zhenyu Cai

John Morton

Michael Fogarty

George Andrew Davidson Briggs

Sofia Patomaki

Jan Andries Mol

Simon Schaal

Ying Li

A method of mitigating errors in quantum computing, wherein the method comprises: performing (S) an operation on the state of a qubit in a group of qubits a plurality of times, wherein the operation has a first error rate, and wherein each performance of the operation comprises: performing a first operation comprising: a gate operation, a symmetry operation, and a first basis operation; or performing a second operation comprising: the gate operation, the symmetry operation, and a second basis operation; wherein the first and second basis operations are different basis operations selected from a set of basis operations; and measuring the state of the qubit; wherein the probability of performing the first operation is a first probability, and the probability of performing the second operation is a second probability; obtaining (S) a symmetry measurement for the group of qubits after each performance of the operation using the symmetry operation, wherein the group of qubits comprises a plurality of qubits; wherein the symmetry measurement is a first symmetry outcome if the number of errors is even or a second symmetry outcome if the number of errors is odd; obtaining (S) a first state measurement by determining the average state of the qubit for the first symmetry outcome; obtaining (S) a second state measurement by determining the average state of the qubit for the second symmetry outcome; fitting (S) the first state measurement to a first curve having the form (I); fitting the second state measurement to a second curve having the form (II); wherein n is an error rate and A and γ are fitting parameters; and extrapolating (S) the average state of the qubit at a second error rate using the first and second fitted curves; wherein the second error rate is lower than the first error rate.

Error mitigation techniques

A method of mitigating errors when using a quantum computer comprising: performing Sa first operation () on the state of a qubit a plurality of times; wherein the first operation () has a first error rate (); obtaining Sa first measurement of the average state of the qubit; modifying Sthe error rate of the quantum computer from the first error rate () to a second error rate (); performing Sa second operation () on the state of the qubit a plurality of times; wherein the second operation () has the second error rate (); obtaining Sa second measurement of the average state of the qubit; modifying Sthe error rate of the quantum computer from the second error rate to a third error rate; performing Sa third operation on the state of the qubit a plurality of times; wherein the third operation has the third error rate; obtaining Sa third measurement of the average state of the qubit; modifying Sthe error rate of the quantum computer from the third error rate to a fourth error rate; performing Sa fourth operation on the state of the qubit a plurality of times; wherein the fourth operation has the fourth error rate; obtaining Sa fourth measurement of the average state of the qubit; fitting Sthe first, second, third and fourth measurements to a multi-exponential decay curve (); and extrapolating Sthe average state of the qubit at a fifth error rate () using the fitted curve (), wherein the fifth error rate () is lower than the first, second, third and fourth error rates.

Multi-exponential error extrapolation

Methods are disclosed for controlling charge stability in a device for quantum information processing. According to examples, a device for quantum information processing comprises a first plurality of confinement regions confining spinful charge carriers for use as qudits. The device further comprises a second plurality of confinement regions confining spinful charge carriers, each confinement region of the second plurality of confinement regions adjacent to a confinement region of the first plurality of confinement regions. The device further comprises one or more charge reservoirs, wherein each confinement region of the second plurality of confinement regions is attachable to a charge reservoir. According to examples, a method for controlling charge stability comprises selectively tuning the relative energy levels of the first plurality of confinement regions and adjacent confinement regions of the second plurality of confinement regions such that, if a spinful charge carrier leaks from a confinement region of the first plurality of confinement regions, then the spinful charge carrier is replaced to ensure that the confinement region of the first plurality of confinement regions again contains a spinful charge carrier for use as a qudit. Control apparatus and computer-readable media are also described herein.

Control of charge carriers in quantum information processing architectures

The present disclosure relates to novel memristive devices, uses thereof, and processes for their preparation. In a first aspect, the disclosure provides a quantum memristor, including a first quantum dot (QD) which is capacitively coupled to a second quantum dot (QD), a source electrode, a drain electrode, and a bath electrode, wherein the source electrode and the drain electrode are coupled via quantum tunneling to QDand the bath electrode is coupled via quantum tunneling to QD, and wherein QDis capacitively coupled to either the source electrode or the drain electrode.

Coupled quantum dot memristor

A device for the storage and/or processing of quantum information comprises: a body (), formed from a material having negligible net nuclear or electronic magnetic field; a set of data entities () embedded in said body, each having a plurality of magnetic field states; a set of probes (), offset from the body, arranged to acquire internal phase shifts due to the magnetic fields of said data entities; wherein the probes () are each arranged to move relative to a plurality of data entities () in order that each probe () acquires an internal phase shift from the plurality of data entities (); and means for reading each probe (), thereby establishing a parity of the plurality of data entities ().

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Oxford, United Kingdom

Simon Benjamin