Systems, methods and apparatus for anti-symmetric qubit-coupling

A coupling system comprising:

• a first qubit having a first degree of freedom that is associated with a first basis element and a second degree of freedom that is associated with a second basis element;
• a second qubit having a first degree of freedom that is associated with the first basis element and a second degree of freedom that is associated with the second basis element;
• and
• a coupling device that communicably couples the first degree of freedom of the first qubit with the second degree of freedom of the second qubit, such that the first degree of freedom of the first qubit influences the second degree of freedom of the second qubit.

A coupling system comprising:

• a first superconducting qubit comprising a qubit loop formed by a loop of superconducting material and a compound Josephson junction that interrupts the qubit loop, the compound Josephson junction comprising a closed loop of superconducting material interrupted by at least two Josephson junctions, where the qubit loop and the compound Josephson junction form a closed superconducting current path;
• a second superconducting qubit comprising a qubit loop formed by a loop of superconducting material and a compound Josephson junction that interrupts the qubit loop, the compound Josephson junction comprising a closed loop of superconducting material interrupted by at least two Josephson junctions, where the qubit loop and the compound Josephson junction form a closed superconducting current path;
• and
• a first coupling device that is formed by a closed superconducting current path, wherein the first coupling device includes a first magnetic flux inductor positioned proximate the qubit loop of the first qubit and configured to selectively provide a first mutual inductance coupling the first magnetic flux inductor to the qubit loop of the first qubit, and wherein the first coupling device includes a second magnetic flux inductor positioned proximate the compound Josephson junction of the second qubit and configured to selectively provide a second mutual inductance coupling the second magnetic flux inductor to the compound Josephson junction of the second qubit.

A method of controllably coupling a first qubit to a second qubit by an anti-symmetric coupling device, the first qubit comprising a qubit loop formed by a loop of superconducting material and a compound Josephson junction that interrupts the qubit loop, the compound Josephson junction comprising a closed loop of superconducting material interrupted by at least two Josephson junctions, where the qubit loop and the compound Josephson junction form a closed superconducting current path, the second qubit comprising a qubit loop formed by a loop of superconducting material and a compound Josephson junction that interrupts the qubit loop, the compound Josephson junction comprising a closed loop of superconducting material interrupted by at least two Josephson junctions, where the qubit loop and the compound Josephson junction form a closed superconducting current path, and the anti-symmetric coupling device comprising a closed superconducting current path that is interrupted by at least one Josephson junction, the method comprising:

• coupling a first portion the coupling device to the qubit loop of the first qubit;
• coupling a second portion the coupling device to the compound Josephson junction of the second qubit;
• coupling a magnetic flux signal to the coupling device;
• and
• adjusting the magnetic flux signal.