Quantum metrology, a branch of quantum information science, investigates the fundamental limits of measurement precision and the strategies to attain them using quantum systems. Precise control of such systems has already enhanced measurement technologies across diverse domains, including atomic clocks, magnetometry, and magnetic resonance imaging (MRI). One of the most promising yet still evolving directions is the use of non-classical properties of quantum states, such as entanglement, to surpass classical precision limits. The achievable precision in any measurement is fundamentally constrained by the Cramér–Rao bound, which provides a simple analytical benchmark for comparing classical and quantum estimation strategies.

In this talk, I will summarize my Ph.D. research, which focuses on implementing quantum metrology protocols in free-space optical platforms. The first experiment demonstrates a superresolution technique that enables the estimation of both the separation and relative intensities of two distant light sources. Such techniques can achieve precisions beyond the diffraction limit, which constrains the resolution of modern telescopes. The second experiment introduces a blueprint for compressing the relative-phase information contained in multiple identical qubits into a single qubit. The scheme is scalable and can be applied to an arbitrary number of qubits. The final experiment utilizes entangled states to optimally characterize dephasing noise, a process that randomizes the relative phase between the terms of a quantum state and leads to decoherence, one of the major challenges in today’s quantum computers.