SYSTEMS AND METHODS FOR ACTIVE NOISE COMPENSATION OF QUBITS

1 . A quantum processor comprising:

a first qubit;

a flux compensation circuit communicatively coupled to the first qubit, the flux compensation circuit comprising:

a quantum flux parametron (QFP) flux pump circuit comprising a first QFP in communication with the first qubit, the first QFP comprising a first Josephson junction;

a storage circuit comprising a second Josephson junction and a storage loop coupled in series with the QFP flux pump circuit, the communication between the QFP flux pump circuit and the storage loop mediated by the second Josephson junction;

a first control line in communication with the first Josephson junction; and

a second control line in communication with the second Josephson junction;

wherein the storage loop is communicatively coupled to the first qubit such that, in use, flux stored in the storage loop back acts on the first qubit.

2 . The quantum processor of claim 1 , wherein the storage loop is communicatively coupled to the first qubit through the first QFP.

3 . The quantum processor of claim 1 , wherein the first Josephson junction and the second Josephson junction each comprise compound Josephson junctions.

4 . The quantum processor of claim 1 , wherein the QFP flux pump circuit comprises a second QFP coupled in series with the first QFP, the second QFP comprising a third Josephson junction, the first QFP and the second QFP connected by an inductor.

5 . The quantum processor of claim 4 , wherein the QFP flux pump circuit comprises a third QFP coupled in series with the second QFP, the coupling between the second QFP and the third QFP mediated by a fourth Josephson junction.

6 . The quantum processor of claim 5 , further comprising a third control line in communication with the third Josephson junction and a fourth control line in communication with the fourth Josephson junction.

7 . The quantum processor of claim 6 , wherein the third Josephson junction and the fourth Josephson junction each comprise compound Josephson junctions.

8 . The quantum processor of claim 1 , wherein the quantum processor comprises a set of qubits, the first qubit being one of the qubits of the set of qubits, and wherein each qubit of the set of qubits is coupled to a respective flux compensation circuit.

9 . The quantum processor of claim 1 , wherein the storage loop comprises a high kinetic inductance material.

10 . A flux compensation circuit comprising:

a quantum flux parametron (QFP) flux pump circuit comprising:

a first QFP, the first QFP comprising a first Josephson junction;

a second QFP connected in series with the first QFP, the second QFP comprising a third Josephson junction, the first QFP and the second QFP connected by an inductor;

a third QFP connected in series with the second QFP, the connection between the second QFP and the third QFP mediated by a fourth Josephson junction;

a storage circuit comprising a second Josephson junction and a storage loop connected in series with the QFP flux pump circuit, the connection between the QFP flux pump circuit and the storage loop mediated by the second Josephson junction;

a first control line in communication with the first Josephson junction;

a second control line in communication with the second Josephson junction;

a third control line in communication with the third Josephson junction; and

a fourth control line in communication with the fourth Josephson junction.

11 . The flux compensation circuit of claim 10 , wherein each of the first, second, third, and fourth Josephson junctions comprise compound Josephson junctions.

12 . The flux compensation circuit of claim 10 , wherein the storage loop comprises a high kinetic inductance material.

13 . A method of compensating flux noise in a qubit, the method comprising:

iteratively, until an exit condition is met:

projecting information about a flux state of the qubit into a quantum flux parametron (QFP) flux pump circuit;

copying the information about the flux state of the qubit through the QFP flux pump circuit as a directional current;

activating a Josephson junction coupled in series with the QFP flux pump circuit to store flux in a storage loop connected to the Josephson junction based on the directional current; and

evaluating the exit condition; and

communicating the flux stored in the storage loop with the qubit to reduce the flux state of the qubit.

14 . The method of claim 13 , wherein projecting information about the flux state of the qubit into a QFP flux pump circuit comprises annealing the qubit in a presence of ambient flux noise.

15 . The method of claim 13 , wherein projecting information about the flux state of the qubit into a QFP flux pump circuit comprises annealing a first QFP in communication with the qubit in a presence of ambient flux noise.

16 . The method of claim 13 , wherein copying the information about the flux state of the qubit through the QFP flux pump circuit as a directional current comprises:

inducing a current in a first QFP comprising a first Josephson junction based on the projected information about the flux state;

activating the first Josephson junction to latch the first QFP;

inducing a current in a second QFP comprising a second Josephson junction based on the current in the latched first QFP; and

activating the second Josephson junction to latch the second QFP.

17 . The method of claim 16 , wherein copying the information about the flux state of the qubit through the QFP flux pump circuit as a directional current further comprises:

inducing a current in a third QFP comprising a third Josephson junction based on the current in the latched second QFP; and

activating the third Josephson junction to latch the third QFP.

18 . The method of claim 13 , wherein evaluating the exit condition comprises incrementing a counter until a number of iterations have been performed.

19 . The method of claim 13 , further comprising deactivating biasing devices in communication with the qubit to isolate the qubit prior to projecting information about the flux state of the qubit.

20 . A method of compensating flux noise in a quantum processor, the quantum processor comprising a plurality of qubits, the method comprising performing the method of any one of claims 13 through 19 for each qubit in the quantum processor.