Mach-Zehnder interferometry in a strongly driven superconducting qubit.

Area of Science:

• Quantum Computing
• Superconducting Circuits
• Quantum Optics

Background:

• Superconducting flux qubits are tunable artificial atoms with distinct ground and excited states.
• These states exhibit an avoided crossing, a critical feature for quantum manipulation.
• Strong harmonic driving of the qubit causes it to traverse this avoided crossing twice per period.

Purpose of the Study:

• To demonstrate Mach-Zehnder-type interferometry in a superconducting flux qubit.
• To explore quantum interference fringes generated by Landau-Zener transitions.
• To provide an alternative method for manipulating and characterizing qubits in a strongly driven regime.

Main Methods:

• Utilizing Mach-Zehnder-type interferometry with a superconducting flux qubit.
• Employing strong harmonic excitation to drive the qubit through its avoided crossing.
• Leveraging Landau-Zener transitions as coherent beamsplitters for phase accumulation.

Main Results:

• Observed quantum interference fringes for transitions involving 1 to 20 photons.
• Demonstrated that accumulated phase varies with microwave amplitude.
• Showcased the generalization of optical Mach-Zehnder interferometry in qubit phase space.

Conclusions:

• Mach-Zehnder-type interferometry is feasible in superconducting flux qubits.
• This technique offers a novel approach to qubit manipulation and characterization.
• The study highlights the quantum optical nature of qubit dynamics in the strongly driven regime.