Ancilla-assisted quantum process tomography

Area of Science:

• Quantum Information Science
• Quantum Optics
• Quantum Computing

Background:

• Complete characterization of quantum dynamical processes is crucial for quantum information science.
• Quantum process tomography (QPT) is a key method for achieving this characterization.

Purpose of the Study:

• To implement and investigate various QPT methods using a correlated photon source.
• To theoretically determine the conditions for ancilla-assisted process tomography (AAPT).
• To compare the effectiveness of AAPT with separable and entangled input states.

Main Methods:

• Utilized a source of correlated photons to implement multiple quantum process tomography techniques.
• Developed theoretical conditions for the feasibility of ancilla-assisted process tomography (AAPT).
• Experimentally tested AAPT using both separable and entangled photon states.

Main Results:

• Successfully implemented several QPT methods, including those for unitary, decohering, and polarizing processes.
• Demonstrated that ancilla-assisted process tomography (AAPT) does not fundamentally require entanglement.
• Observed that using entangled input states leads to improved results in AAPT.

Conclusions:

• Ancilla-assisted process tomography (AAPT) offers a viable route for quantum process characterization.
• The findings challenge the necessity of entanglement for AAPT, broadening its applicability.
• Entanglement remains a valuable resource for enhancing the precision of quantum process tomography.