No description available.

No description available.

No description available.

Thesis (Ph.D.)--Australian National University, 2001.

As a subset of quantum optics, single photons are one of the competing physical resources for quantum information processing. When used as carriers of quantum information, they have no equal. For the processing of quantum information, single photons have proven difficult to scale beyond the order of ⇠ 10 photons. The lack of single-photon-level interaction has led to creative approaches which rely on postselection to filter the possible measured outcomes to those which appear as though interaction occurred. This approach of post-selection leans heavily on the ability to not only generate but also detect scores of single photons simultaneously and with near perfect efficiency. Our work relaxes the emphasis which has been placed on single photons for quantum information processing to that of states with, in principle, an arbitrary number of photons. Central moment expectations on two-mode squeezed states are shown to exhibit post-selection behavior which reflects the single-photon counterpart. These measures are proven to be robust to loss and return entangled state statistics on average. With naive estimation of the central moment, states with ~ 20 modes are within reach with current technology, closing the gap between quantum states which can and cannot be classically simulated. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

Fazendo uso da equivalência entre um potencial não-local e um potencial dependente da velocidade, mostramos como construir um potencial não-local capaz de gerar estados comprimidos. No contexto do modelo de Jaynes-Cummings que descreve a interação quântica de um único átomo de dois níveis com um único modo do campo eletromagnético quantizado, mostrando uma nova característica no comportamento dinâmico da inversão atômica, quando o campo é preparado em um estado coerente comprimido par. Usando o modelo de Jaynes-Cummings propomos um método para estudar o estado quântico e a variância do operador de fase, através da medida da distribuição de momento de átomos espalhados, proveniente da interação de um feixe atômico com um único modo do campo eletromagnético via interação de dois fótons. / Exploring the equivalence between a non-local and a velocity-dependent potential we show how to construct a non-local potential, which is able to generate squeezed states. In the context of the Jaynes-Cummings model we describe the quantum interaction of a single two-level atom with a single mode of a quantum electromagnetic field, showing a new feature in the dynamical behavior of atomic inversion when the electromagnetic field is prepared in an even squeezed coherent state. By using the Jaynes-Cummings model, a method to study quantum state and variance of the phase operator is proposed. The method consists in measuring the momentum distribution of atoms resulting from the interaction of a prepared atomic beam with a single mode electromagnetic field via two-photon interaction.

No description available.

The performance of optical measurement systems is ultimately limited by the quantum nature of light. In this thesis, two techniques for circumventing the standard quantum measurement limits are modelled and tested experimentally. These techniques are electro-optic control and the use of squeezed light. An optical parametric amplifier is used to generate squeezing at 1064nm. The parametric amplifier is pumped by the output of a second harmonic generation cavity, which in turn is pumped by a Nd:YAG laser. By using various frequency locking techniques, the quadrature phase of the squeezing is stabilised, therefore making our squeezed source suitable for long term measurements. The best recorded squeezing is 5.5dB (or 70\%) below the standard quantum limit. The stability of our experiment makes it possible to perform a time domain measurement of photocurrent correlations due to squeezing. This technique allows direct visualisation of the quantum correlations caused by squeezed light. On the road to developing our squeezed source, methods of frequency locking optical cavities are investigated. In particular, the tilt locking method is tested on the second harmonic generation cavity used in the squeezing experiment. The standard method for locking this cavity involves the use of modulation sidebands, therefore leading to a noisy second harmonic wave. The modulation free tilt-locking method, which is based on spatial mode interference, is shown to be a reliable alternative. In some cases, electro-optic control may be used to suppress quantum measurement noise. Electro-optic feedback is investigated as a method for suppressing radiation pressure noise in an optical cavity. Modelling shows that the `squashed' light inside a feedback loop can reduce radiation pressure noise by a factor of two below the standard quantum limit. This result in then applied to a thermal noise detection system. The reduction in radiation pressure noise is shown to give improved thermal noise sensitivity, therefore proving that the modified noise properties of light inside a feedback loop can be used to reduce quantum measurement noise. Another method of electro-optic control is electro-optic feedforward. This is also investigated as a technique for manipulating quantum measurements. It is used to achieve noiseless amplification of a phase quadrature signal. The results clearly show that a feedforward loop is a phase sensitive amplifier that breaks the quantum limit for phase insensitive amplification. This experiment is the first demonstration of noiseless phase quadrature amplification. Finally, feedforward is explored as a tool for improving the performance of quantum nondemolition measurements. Modelling shows that feedforward is an effective method of increasing signal transfer efficiency. Feedforward is also shown to work well in conjunction with meter squeezing. Together, meter squeezing and feedforward provide a comprehensive quantum nondemolition enhancement package. Using the squeezed light from our optical parametric amplifier, an experimental demonstration of the enhancement scheme is shown to achieve record signal transfer efficiency of $T_{s}+T_{m}=1.81$.

Thesis (M.S.)--Rutgers University, 2007. / "Graduate Program in Electrical and Computer Engineering." Includes bibliographical references (p. 259-263).

Fazendo uso da equivalência entre um potencial não-local e um potencial dependente da velocidade, mostramos como construir um potencial não-local capaz de gerar estados comprimidos. No contexto do modelo de Jaynes-Cummings que descreve a interação quântica de um único átomo de dois níveis com um único modo do campo eletromagnético quantizado, mostrando uma nova característica no comportamento dinâmico da inversão atômica, quando o campo é preparado em um estado coerente comprimido par. Usando o modelo de Jaynes-Cummings propomos um método para estudar o estado quântico e a variância do operador de fase, através da medida da distribuição de momento de átomos espalhados, proveniente da interação de um feixe atômico com um único modo do campo eletromagnético via interação de dois fótons. / Exploring the equivalence between a non-local and a velocity-dependent potential we show how to construct a non-local potential, which is able to generate squeezed states. In the context of the Jaynes-Cummings model we describe the quantum interaction of a single two-level atom with a single mode of a quantum electromagnetic field, showing a new feature in the dynamical behavior of atomic inversion when the electromagnetic field is prepared in an even squeezed coherent state. By using the Jaynes-Cummings model, a method to study quantum state and variance of the phase operator is proposed. The method consists in measuring the momentum distribution of atoms resulting from the interaction of a prepared atomic beam with a single mode electromagnetic field via two-photon interaction.