M.Sc Thesis

M.Sc StudentRosenblum Serge
SubjectGeneration and Nondemolition Measurement of Complex Photon
DepartmentDepartment of Electrical and Computer Engineering
Supervisor PROF. Meir Orenstein
Full Thesis textFull thesis text - English Version


Qubits, which are the basic information units of future quantum computers, can be roughly classified into two subsets: flying qubits, which are characterized by robustness against interaction with the environment, and stationary qubits, which enable interactions between various qubits. The paradigm of the first subset is the photon. Photons, when off-resonance with the environment, can travel large distances at high speed with low loss. Carrying information from one location to another is therefore most easily done with photons. However, when storage, measurement and computation are to be performed, the photonic qubits need to be converted into stationary qubits. Often atoms are used for this purpose, mainly because they are relatively easy to localize. Producing the interface between the two types of qubits proves to be a significant bottleneck to the progress of quantum information technology. The reason is that photons hardly interact with atomic systems, and when they do interact, they usually lose their information, since the coherent phases between the various particles involved are lost. This work focuses on two subjects where both a strong interaction between light and matter, and the ability to create output containing useful information are required.

In the first part we propose a device that measures photon hole (PH) signals nondestructively. PHs are temporal decreases of the photon detection probability in an otherwise stationary background of light. The scheme is based on electromagnetically induced transparency in a medium irradiated by signal and probe beams. The background signal light is not affected, while the presence of a PH in the signal beam results in a delay of the probe. Thus, information is copied coherently from the PH signal to the probe through the atomic system, while the PH itself is left unaffected. We also propose a system that creates time-energy entangled pairs of PHs and photons, and look for a way to demonstrate their entanglement.

The second part is dedicated to the proposal of a solid-state source of hyperentangled photons, emitting photon pairs entangled in both energy and polarization. Solid-state entangled photon sources usually have low generation rates, since they operate off-resonance. The proposed source is compact, electrically driven, and exhibits pair generation rates up to five orders of magnitude higher than alternative conventional schemes. This is achieved by using light created by intersubband two-photon emission from semiconductor quantum wells. A theoretical formalism is derived for the calculation of photon pair generation spectra and rates.