Selective and efficient quantum process tomography with single photons.

Area of Science:

• Quantum Information Science
• Quantum Optics
• Quantum Computing

Background:

• Quantum process tomography is crucial for characterizing quantum systems.
• Existing methods often require resources that scale exponentially with the number of qubits.
• Efficient characterization is vital for developing scalable quantum technologies.

Purpose of the Study:

• To present the first photonic implementation of a novel quantum process tomography method.
• To demonstrate a method with resources scaling polynomially with the number of qubits.
• To compare the new method's performance and advantages against existing techniques.

Main Methods:

• Implementing a new quantum process tomography algorithm using a heralded single photon source.
• Mapping chi-matrix element estimation to average fidelity estimation of a quantum channel.
• Utilizing a 2-design for random sampling to estimate quantum channel fidelity.

Main Results:

• Successful full photonic implementation of the quantum process tomography algorithm.
• Process tomography performed on channels affecting a polarization qubit.
• Demonstration of polynomial resource scaling for estimating chi-matrix elements.

Conclusions:

• The photonic implementation validates the efficiency of the new quantum process tomography method.
• The method offers a significant advantage in resource scaling compared to previous approaches.
• This technique advances the practical application of quantum process characterization.