Brillouin Cooling

We analyze how to exploit Brillouin scattering for the purpose of cooling opto-mechanical devices and present a quantum-mechanical theory for Brillouin cooling. Our analysis shows that significant cooling ratios can be obtained with standard experimental parameters. A further improvement of cooling efficiency is possible by increasing the dissipation of the optical anti-Stokes resonance.Comment: 4 pages 3 figure

Quantum Cloning of Binary Coherent States - Optimal Transformations and Practical Limits

The notions of qubits and coherent states correspond to different physical systems and are described by specific formalisms. Qubits are associated with a two-dimensional Hilbert space and can be illustrated on the Bloch sphere. In contrast, the underlying Hilbert space of coherent states is infinite-dimensional and the states are typically represented in phase space. For the particular case of binary coherent state alphabets these otherwise distinct formalisms can equally be applied. We capitalize this formal connection to analyse the properties of optimally cloned binary coherent states. Several practical and near-optimal cloning schemes are discussed and the associated fidelities are compared to the performance of the optimal cloner.Comment: 12 pages, 12 figure

Pismo Clams (Tivela stultorum) in Califorina: Population Status, Habitat Associations, Reproduction, and Growth

Marine shellfish play a vital role in intertidal ecosystems and coastal communities, but many of these fisheries are small-scale and lack the necessary monitoring to ensure long-term sustainability. Effective management often requires information on key demographic parameters, such as population status, reproduction and growth. Pismo clams (Tivela stultorum) are a culturally important and iconic species in California, which supported a thriving commercial and recreational fishery throughout much of the 1900’s. However, Pismo clam populations have declined statewide in recent decades and are attributed to human harvest and predation by California sea otters (Enhydra lutris); However, no studies have examined their populations, population drivers, or life history for at least 40 years. Managers require updated and expanded information on populations, habitat associations, reproduction and growth rates to effectively manage, regulate, and recover Pismo clam in California. In Chapter 1, we investigated current Pismo clam population levels in California and examined the role of abiotic and biotic factors as correlates of clam abundance. We quantified Pismo clam presence, density and biomass at 38 sites in California during 2018 and 2019. Our results indicate that while human population density does not appear to drive clam populations, median sediment grain size is an important predictor for Pismo clams on open coast beaches. As median grain size increases, the probability of clam presence, density, and biomass decreases, suggesting that the composition of beach habitat is a critical factor regulating Pismo clam populations. Additionally, clam density and biomass are significantly higher on beaches north of Point Conception compared to beaches south. This suggests that Pismo clam population declines are more complicated than conventional wisdom suggests. Overall, Pismo clam densities are lower and size structures are shifted towards smaller sizes than historical accounts. This study is the most comprehensive set of population surveys to date and identifies key factors associated with Pismo clam abundance, which may be used to inform management and guide restoration and recovery of this once iconic species. In Chapter 2, we examined life history characteristics of Pismo clams in California. Specifically, we investigated the annual reproductive cycle of Pismo clams in California, pairing multiple metrics within a single study to describe the sex ratio, gonad development stages, body condition index, and length at sexual maturity. Further, we examine age-length relationships across California to provide estimates of age structure and growth rate, which will better inform recovery timelines for the recreational fishery in California. Our results indicate that the sex ratio is 1:1, peak spawning occurred in late summer, and clams can spawn in their first year (\u3c20 \u3emm). Cycles of body condition were influenced primarily by mean monthly sea surface temperature, but mean monthly chlorophyll-a concentration, photoperiod, clam size, and year were also important. Body condition was significantly correlated with the proportion of clams in the Ripe stage. Thus, body condition has the potential to be a rapid, inexpensive proxy for monitoring reproduction in Pismo clams, potentially providing useful information about changes in reproductive patterns. Finally, examination of age-length relationships for Pismo clams suggest that clams may require over 13 years to reach a legally harvestable size (114 mm across most of California). The estimated age at legal size is substantially older than historical estimates, which suggested that Pismo clams could reach legally harvestable size in as few as 6 years. Collectively, this work represents a significant advance in our knowledge of the biology and ecology of this iconic and culturally important species. Furthermore, it provides vital information on the current population status, reproduction, and growth rates to inform management, regulation, and potential recovery of Pismo clams in California

Exploiting the nonlinear impact dynamics of a single-electron shuttle for highly regular current transport

The nanomechanical single-electron shuttle is a resonant system in which a suspended metallic island oscillates between and impacts at two electrodes. This setup holds promise for one-by-one electron transport and the establishment of an absolute current standard. While the charge transported per oscillation by the nanoscale island will be quantized in the Coulomb blockade regime, the frequency of such a shuttle depends sensitively on many parameters, leading to drift and noise. Instead of considering the nonlinearities introduced by the impact events as a nuisance, here we propose to exploit the resulting nonlinear dynamics to realize a highly precise oscillation frequency via synchronization of the shuttle self-oscillations to an external signal.Comment: 5 pages, 4 figure

Decoherence induced by an interacting spin environment in the transition from integrability to chaos

We investigate the decoherence properties of a central system composed of two spins 1/2 in contact with a spin bath. The dynamical regime of the bath ranges from a fully integrable integrable limit to complete chaoticity. We show that the dynamical regime of the bath determines the efficiency of the decoherence process. For perturbative regimes, the integrable limit provides stronger decoherence, while in the strong coupling regime the chaotic limit becomes more efficient. We also show that the decoherence time behaves in a similar way. On the contrary, the rate of decay of magnitudes like linear entropy or fidelity does not depend on the dynamical regime of the bath. We interpret the latter results as due to a comparable complexity of the Hamiltonian for both the integrable and the fully chaotic limits.Comment: Submitted to Phys. Rev.

Introduction to Quantum Noise, Measurement and Amplification

The topic of quantum noise has become extremely timely due to the rise of quantum information physics and the resulting interchange of ideas between the condensed matter and AMO/quantum optics communities. This review gives a pedagogical introduction to the physics of quantum noise and its connections to quantum measurement and quantum amplification. After introducing quantum noise spectra and methods for their detection, we describe the basics of weak continuous measurements. Particular attention is given to treating the standard quantum limit on linear amplifiers and position detectors using a general linear-response framework. We show how this approach relates to the standard Haus-Caves quantum limit for a bosonic amplifier known in quantum optics, and illustrate its application for the case of electrical circuits, including mesoscopic detectors and resonant cavity detectors.Comment: Substantial improvements over initial version; include supplemental appendices

TIRS Cryocooler: Spacecraft Integration and Test and Early Flight Data

The Thermal Infrared Sensor (TIRS) is an instrument on Landsat 8, launched in February 2013. The focal plane is cooled by a two-stage Ball Aerospace Stirling cycle cryocooler, with a coldfinger operating at 40K. This paper describes events during the spacecraft integration and test program, and results from early orbit operation of the cryocooler

Electrothermal flow in Dielectrophoresis of Single-Walled Carbon Nanotubes

We theoretically investigate the impact of the electrothermal flow on the dielectrophoretic separation of single-walled carbon nanotubes (SWNT). The electrothermal flow is observed to control the motions of semiconducting SWNTs in a sizeable domain near the electrodes under typical experimental conditions, therefore helping the dielectrophoretic force to attract semiconducting SWNTs in a broader range. Moreover, with the increase of the surfactant concentration, the electrothermal flow is enhanced, and with the change of frequency, the pattern of the electrothermal flow changes. It is shown that under some typical experimental conditions of dielectrophoresis separation of SWNTs, the electrothermal flow is a dominating factor in determining the motion of SWNTs.Comment: 5 pages, 4 figures, Submitted to PR

Gradient Ascent Pulse Engineering with Feedback

Efficient approaches to quantum control and feedback are essential for quantum technologies, from sensing to quantum computation. Pure control tasks have been successfully solved using optimization techniques, including methods like gradient-ascent pulse engineering (GRAPE) , relying on a differentiable model of the quantum dynamics. For feedback tasks, such methods are not directly applicable, since the aim is to discover strategies conditioned on measurement outcomes. There, model-free reinforcement learning (RL) has recently proven a powerful new ansatz. What is missing is a way to combine the best of both approaches for scenarios that go beyond weak measurements. In this work, we introduce feedback-GRAPE, which borrows concepts from model-free RL to incorporate the response to strong stochastic (discrete or continuous) measurements, while still performing direct gradient ascent through the quantum dynamics. We illustrate its power on a Jaynes-Cummings model with feedback, where it yields interpretable feedback strategies for state preparation and stabilization in the presence of noise. This approach could be employed for discovering strategies in a wide range of feedback tasks, from calibration of multi-qubit devices to linear-optics quantum computation strategies, quantum-enhanced sensing with adaptive measurements, and quantum error correction