Dissertations and Theses

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The aim of this research is to study imaging techniques using quantum entangled qubits. These techniques extract information about the quantum state of two entangled qubits and corelate the degree of entanglement to each pixel. Imaging information of the underlying structure or material is decoded using the reconstruction of the quantum density matrix along with the calculated entanglement and concurrence levels between the two qubits. Reconstruction of a quantum state and quantum state tomography are of increasing importance in quantum information science. Quantum state tomography is used to describe entanglement of trapped ions [1] and photons [2]. Number of experiments were demonstrated in quantum computing, quantum communication and quantum networks where the quantum state density matrix was reconstructed from a set of experimental measurements [2-11]. It is also clear that quantum sensing, quantum computing and quantum imaging techniques can outperform current classical systems in certain areas [12-15]. Yet very little work was done to experimentally apply quantum imaging techniques to study and image birefringent materials. In 1935, Einstein, Podolsky and Rosen published the famous EPR paradox [16], underlining the incomplete description of physical reality and the requirement of hidden variables. The phenomenon involved quantum entanglement and it opened opportunities for research in numerous fields of study. In optical communication entangled states were applied to quantum information theory, quantum teleportation and quantum cryptography [16-29]. Probably the most popular applications are in quantum computing. The superposition of entangled states represents quantum bits in combination of both logical one and zero simultaneously. For the last few decades, very few experiments were conducted to utilize quantum entanglement in imaging or material characterization applications. The proposed study develops and describes quantum imaging and characterization techniques using the increased sensitivity and quantum-entanglement of the bosonic states. Quantum mechanics accommodates co-existence of two completely indistinguishable photon particles separated in space. One of the entangled photons can be made to interact with the investigated sample. The sample is placed on a microscope slide and scanned in the transverse and/or axial plane. The localized birefringence changes the polarization of the photon, and these changes translate into a reduction of the coincidence rate of the entangled photons. This research also presents the first experimental imaging implementation of polarization sensitive quantum optical coherence tomography (PS-QOCT), a technique introduced years ago by a group at Boston University. The idea is simple enough: it consists of a fourth-order interferometric technique that uses quantum-entangled photons, generated in a type-II crystal via spontaneous parametric down-conversion. In contrast with its classical counterpart, PS-QOCT provides resolution enhancement and immunity to even- order group velocity dispersion. A proof-of-principle of this technique was demonstrated a while ago [30] using a type-II collinear phase-matching in a BBO crystal pumped by a Ti:Shapphire picosecond pulsed laser source. However, imaging measurements have not been reported in [30]. The work in this thesis provides the missing data. The goal of this research work was to develop and study quantum imaging techniques. Apply entangled qubits to characterize birefringence and reconstruct images from entanglement and concurrence levels. Quantum imaging technique was also used to examine healthy and cancerous human lung tissues. Well- defined concurrence and entanglement images of birefringence were obtained in lung tissue with melanoma while no birefringence was detected in healthy samples. Melanoma is an aggressive tumor and has a propensity to metastasize to lymph nodes in lungs, liver and virtually any other site of the body. Our work suggests that quantum imaging could eventually assist with the medical diagnosis of metastatic melanoma in the future.



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