arXiv subjects

B. T. H. Varcoe

Publications and source records attributed to B. T. H. Varcoe.

8 recordsLinked to original sources

arXiv2011

A three step laser stabilisation scheme for excitation to Rydberg levels in 85Rb

We demonstrate a three step laser stabilisation scheme for excitation to nP and nF Rydberg states in 85Rb, with all three lasers stabilised using active feedback to independent Rb vapour cells. The setup allows stabilisation to the Rydberg states 36P3/2 to 70P3/2 and 33F7/2 to 90F7/2, with the only limiting factor being the available third step laser power. We study the scheme by monitoring the three laser frequencies simultaneously against a self-referenced optical frequency comb. The third step laser, locked to the Rydberg transition, displays an Allan deviation of 30 kHz over 1 second and < 80 kHz over 1 hour. The scheme is very robust and affordable, and it would be ideal for carrying out a range of quantum information experiments.

quant-ph↗

arXiv2010

Absolute frequency measurements of 85Rb nF7/2 Rydberg states using purely optical detection

A three-step laser excitation scheme is used to make absolute frequency measurements of highly excited nF7/2 Rydberg states in 85Rb for principal quantum numbers n=33-100. This work demonstrates the first absolute frequency measurements of rubidium Rydberg levels using a purely optical detection scheme. The Rydberg states are excited in a heated Rb vapour cell and Doppler free signals are detected via purely optical means. All of the frequency measurements are made using a wavemeter which is calibrated against a GPS disciplined self-referenced optical frequency comb. We find that the measured levels have a very high frequency stability, and are especially robust to electric fields. The apparatus has allowed measurements of the states to an accuracy of 8.0MHz. The new measurements are analysed by extracting the modified Rydberg-Ritz series parameters.

quant-ph↗

arXiv2009

Evolutionary Optimization of State Selective Field Ionization for Quantum Computing

State selective field ionization detection techniques in physics require a specific progression through a complicated atomic state space to optimize state selectivity and overall efficiency. For large principle quantum number n, the theoretical models become computationally intractable and any results are often rendered irrelevant by small deviations from ideal experimental conditions, for example external electromagnetic fields. Several different proposals for quantum information processing rely heavily upon the quality of these detectors. In this paper, we show a proof of principle that it is possible to optimize experimental field profiles in situ by running a genetic algorithm to control aspects of the experiment itself. A simple experiment produced novel results that are consistent with analyses of existing results.

physics.ins-det↗

arXiv2009

The Standard Model Extension For a Modified Ives-Stillwell Test

In this paper we present the full theoretical model of a modified Ives-Stillwell experiment where counter propagating lasers are used to form a narrow interference fringe when the lasers form a double resnonance. This narrow resoannce can be as small as 1 Hz wide and therefore provides a connection between the atomic resonance in its rest frame and the laser frequency in the lab frame. The current paper builds on a simplified approach suggested recently and presents a fully developed theory of the interaction within the Lorentz vilating electrodynamics of the Standard Model Extension.

quant-ph↗

arXiv2009

Precision measurements of quantum defects in the $n$P$_{3/2}$ Rydberg States of ${}^{85}$Rb

Rydberg States are used in our One Atom Maser experiment because they offer a large dipole moment and couple strongly to low numbers of microwave photons in a high Q cavity. Here we report the absolute frequencies of the P$_{3/2}$ states for principal quantum numbers $n=36$ to $n=63$. These measurements were made with a three step laser excitation scheme. A wavemeter was calibrated against a frequency comb to provide accurate absolute frequency measurements over the entire range, reducing the measurement uncertainty to 1MHz. We compare the spectroscopic results with known frequency measurements as a test of measurement accuracy.

quant-ph↗

arXiv2009

Single microwave photon detection in the micromaser

High efficiency single photon detection is an interesting problem for many areas of physics, including low temperature measurement, quantum information science and particle physics. For optical photons, there are many examples of devices capable of detecting single photons with high efficiency. However reliable single photon detection of microwaves is very difficult, principally due to their low energy. In this paper we present the theory of a cascade amplifier operating in the microwave regime that has an optimal quantum efficiency of 93%. The device uses a microwave photon to trigger the stimulated emission of a sequence of atoms where the energy transition is readily detectable. A detailed description of the detector's operation and some discussion of the potential limitations of the detector are presented.

quant-ph↗

arXiv2006

Axion Detection in the Micromaser

We report on a scheme for highly efficient detection of single microwave photons, with application to detecting certain exotic particles such as the axion. This scheme utilises an experiment known as the micromaser and the phenomenon of trapping states to amplify the signal and produce a cascade of detector counts in a field ionization detector. The cascade provides a time-resolved signal marking the presence of a single photon. For experimentally achievable parameters, the detection efficiency exceeds 90 percent.

physics.ins-det↗

arXiv1999

Quantum State Reconstruction Using Atom Optics

We present a novel technique in which the total internal quantum state of an atom may be reconstructed via the measurement of the momentum transferred to an atom following its interaction with a near resonant travelling wave laser beam. We present the first such measurement and demonstrate the feasibility of the technique.

quant-ph↗