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A circuit comprising a superconducting qubit and a resonant control system that is characterized by a resonant frequency. The resonant frequency of the control system is a function of a bias current. The circuit further includes a superconducting mechanism having a capacitance or inductance. The sup

A circuit comprising a superconducting qubit and a resonant control system that is characterized by a resonant frequency. The resonant frequency of the control system is a function of a bias current. The circuit further includes a superconducting mechanism having a capacitance or inductance. The superconducting mechanism coherently couples the superconducting qubit to the resonant control system. A method for entangling a quantum state of a first qubit with the quantum state of a second qubit. In the method, a resonant control system, which is capacitively coupled to the first and second qubit, is tuned to a first frequency that corresponds to the energy differential between the lowest two potential energy levels of the first qubit. The resonant control system is then adjusted to a second frequency corresponding to energy differential between the lowest two potential energy levels of the second qubit.

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1. A method for entangling a quantum stat of a first qubit with a quantum state of a second qubit, the method comprising:tuning a resonant control system, which is capacitively or inductively coupled to said first qubit and said second qubit, to a first frequency for a first period of time, wherein

1. A method for entangling a quantum stat of a first qubit with a quantum state of a second qubit, the method comprising:tuning a resonant control system, which is capacitively or inductively coupled to said first qubit and said second qubit, to a first frequency for a first period of time, wherein said first frequency corresponds to an energy differential between a first potential energy level and a second potential energy level of said first qubit; and adjusting said resonant control system to a second frequency for a second period of time, wherein said second frequency corresponds to an energy differential between a first potential energy level and a second potential energy level of said second qubit, thereby entangling the quantum state of the first qubit with the quantum state of the second qubit. 2. The method of claim 1, wherein said resonant control system is an anharmonic resonator.3. The method of claim 1, wherein said resonant control system is superconducting.4. The method of claim 1, wherein said resonant control system comprises a Josephson junction and a bias current source that is connected in series with the Josephson junction, and wherein said tuning and adjusting comprise altering a magnitude of said bias current source.5. The method of claim 4, wherein said bias current source is 0.994*Ic or less during said tuning and adjusting, wherein Ic is the critical current of said Josephson junction.6. The method of claim 4, wherein said bias current source is 0.990*Ic or less during said tuning and adjusting, wherein Ic is the critical current of said Josephson junction.7. The method of claim 1, wherein said first period of time is one microsecond or less.8. The method of claim 1, wherein said first period of time is one hundred nanoseconds or less.9. The method of claim 1, wherein said first qubit is a different type of qubit than said second qubit.10. The method of claim 1, wherein a length of said first period of time is a function of a length of said second period of time.11. The method of claim 1, wherein said first period of time is long enough for said resonant control system to entangle with a quantum state of said first qubit.12. The method of claim 1, wherein said second period of time is one microsecond or less.13. The method of claim 1, wherein said second period of time is one hundred nanoseconds or less.14. The method of claim 1, wherein a length of said second period of time is a function of a length of said first period of time.15. The method of claim 1, wherein a length of said second period of time is a length of time that is sufficient for the resonant control system to entangle with the quantum state of said second qubit.16. The method of claim 1, the method further comprisingapplying a first quantum gate to said first qubit prior to said tuning; and applying a second quantum gate to said first qubit after said tuning. 17. The method of claim 16 wherein said first quantum gate is a Hadamard gate and said second quantum gate is a Hadamard gate.18. The method of claim 1, the method further comprising:applying a first quantum gate to said second qubit prior to said adjusting; and applying a second quantum gate to said second qubit after said adjusting. 19. The method of claim 18 wherein said first quantum gate is a Hadamard gate and said second quantum gate is a Hadamard gate.20. The method of claim 1, wherein said first qubit, said second qubit, or both said first qubit and said second qubit are described by native interaction Hamiltonian that includes an off diagonal interaction term.21. The method of claim 20, wherein said first qubit, said second qubit, or both said first qubit and said second qubit are a superconducting charge qubit.22. The method of claim 1, wherein said first qubit, said second qubit, or both said first qubit and said second qubit are described by a native interaction Hamiltonian that includes a diagonal interaction term.23. The method of claim 22, wherein said first qubit, said second qubit, or both said first qubit and said second qubit is a charge qubit, a phase qubit, or a flux qubit.24. A method for entangling a first qubit in a first qubit group with a second qubit in a second qubit group, the method comprising:(A) coupling, for a first period of time, said first qubit with a first resonant control system by biasing said first resonant control system to a first frequency, said first frequency determined by an energy differential between a first potential energy level and a second potential energy level of said first qubit; (B) coupling, for a second period of time, said first resonant control system to a pivot qubit by biasing said resonant control system to a second frequency, said second frequency determined by an energy differential between a first potential energy level and a second potential energy level of said pivot qubit; (C) isolating said pivot qubit from said first qubit group and said first resonant control system; (D) coupling, for a third period of time, a second resonant control system with said pivot qubit by biasing said second resonant control system to a third frequency, said third frequency determined by said energy differential between said first potential energy level and said second potential energy level of said pivot qubit; wherein said second resonant control system is capacitively or inductively coupled to said second qubit in said second qubit group; (E) isolating said second qubit group and said second resonant control system from said pivot qubit; and (F) coupling, for a fourth period of time, said second resonant control system with said second qubit by biasing said second resonant control system to a fourth frequency, said fourth frequency determined by a first potential energy level and a second potential energy level of said second qubit. 25. The method of claim 24, wherein said first resonant control system is an anharmonic resonator and said second resonant control system is an anharmonic resonator.26. The method of claim 24, wherein said first resonant control system is superconducting and said second resonant control system is superconducting.27. The method of claim 24, wherein said first resonant control system includes a Josephson junction and a bias current source, wherein the bias current source is connected in series with the Josephson junction, and wherein said biasing in said coupling in step (A) and said coupling in step (B) comprises adjusting said bias current source.28. The method of claim 27, wherein said bias current source is 0.994*Ic or less during said coupling in step (A) and said coupling in step (B), and wherein Ic is the critical current of said Josephson junction.29. The method of claim 27, wherein said bias current source is 0.990*Ic or less during said coupling in step (A) and said coupling in step (B), and wherein Ic is the critical current of said Josephson junction.30. The method of claim 24, wherein said second resonant control system comprises a Josephson junction and a bias current source, wherein said bias current source is connected in series with the Josephson junction, and wherein said biasing in said coupling in step (D) and said coupling in step (F) comprises adjusting said bias current source.31. The method of claim 30, wherein said bias current source is 0.994*Ic or less during said coupling in step (D) and said coupling in step (F), and wherein Ic is the critical current of said Josephson junction.32. The method of claim 30, wherein said bias current source is 0.990*Ic or less during said coupling in step (D) and said coupling in step (F), and wherein Ic is the critical current of said Josephson junction.33. The method of claim 24, wherein each of said first period of time, said second period of time, said third period of time, and said fourth period of time is one microsecond or less.34. The method of claim 24, wherein each of said first period of time, said second period of time, said third period of time, and said fourth period of time is one hundred nanoseconds or less.35. The method of claim 24, wherein said first qubit is a different type of qubit than said second qubit.36. The method of claim 24, wherein coupling in step (B) comprises(i) closing a first switch between said first resonant control system and said pivot qubit for a duration greater than said second period of time; and (ii) opening said first switch. 37. The method of claim 24, the method further comprising;(G) coupling said first resonant control system to said first qubit for a period of time equivalent to said first period of time, wherein said coupling is performed after said second period of time has elapsed. 38. The method of claim 24, the method further comprising:(G) coupling said second resonant control circuit to said first pivot qubit for a period of time that is equivalent to said third period of time, wherein said coupling is performed after said fourth period of time has elapsed. 39. The method of claim 24, the method further comprising:(G) applying a first quantum gate to said first qubit prior to said coupling in step (A); and (H) applying a second quantum gate to said first qubit after said coupling in step (A). 40. The method of claim 39, wherein said first quantum gate is a Hadamard gate and said second quantum gate is a Hadamard gate.41. The method of claim 24, the method further comprising:(G) applying a first quantum gate to said second qubit prior to said coupling in step (F); and (H) applying a second quantum gate to said second qubit after said coupling in step (F). 42. The method of claim 41 wherein said first quantum gate is a Hadamard gate and said second quantum gate is a Hadamard gate.43. The method of claim 24, wherein said first qubit, said second qubit, or both said first qubit and said second qubit are described by a native interaction Hamiltonian that includes an off diagonal interaction term.44. The method of claim 43, wherein said first qubit, said second qubit, or both said first qubit and said second qubit are a superconducting charge qubit.45. The method of claim 24, wherein said first qubit, said second qubit, or both said first qubit and said second qubit are described by a native interaction Hamiltonian that includes a diagonal interaction term.46. The method of claim 45, wherein said first qubit, said second qubit, or both said first qubit and said second qubit is a charge qubit, a phase qubit, or a flux qubit.