3,009 research outputs found
Measurement-based quantum control of mechanical motion
Controlling a quantum system based on the observation of its dynamics is
inevitably complicated by the backaction of the measurement process. Efficient
measurements, however, maximize the amount of information gained per
disturbance incurred. Real-time feedback then enables both canceling the
measurement's backaction and controlling the evolution of the quantum state.
While such measurement-based quantum control has been demonstrated in the clean
settings of cavity and circuit quantum electrodynamics, its application to
motional degrees of freedom has remained elusive. Here we show
measurement-based quantum control of the motion of a millimetre-sized membrane
resonator. An optomechanical transducer resolves the zero-point motion of the
soft-clamped resonator in a fraction of its millisecond coherence time, with an
overall measurement efficiency close to unity. We use this position record to
feedback-cool a resonator mode to its quantum ground state (residual thermal
occupation n = 0.29 +- 0.03), 9 dB below the quantum backaction limit of
sideband cooling, and six orders of magnitude below the equilibrium occupation
of its thermal environment. This realizes a long-standing goal in the field,
and adds position and momentum to the degrees of freedom amenable to
measurement-based quantum control, with potential applications in quantum
information processing and gravitational wave detectors.Comment: New version with corrected detection efficiency as determined with a
NIST-calibrated photodiode, added references and revised structure. Main
conclusions are identical. 41 pages, 18 figure
High pulse energy near-infrared ultrafast optical parametric oscillators
A source-demand in the near- and mid-IR wavelength spectrum exists for various applications such as waveguide inscription, multiphoton imaging, and nonlinear spectroscopy. All of the applications seek for higher repetitions rates for faster processing speed, better signal to noise ratios or to improve the results for applications like laser waveguide inscription. This is in contrast to the high pulse energies, required to drive the nonlinear processes involved with these applications. Available systems are either based on low-energy, high-repetition-rate optical parametric oscillators or high-energy, low-repetition-rate optical parametric amplifiers. In this thesis a sources was developed that can bridge the wide gap between these two extremes, providing sufficient energy to drive nonlinear processes, with repetition rates in the MHz domain.
This was achieved by introducing three techniques previously employed for energy scaling in laser cavities. Firstly an exchange from the conventionally used Ti:sapphire pump to a commercial high power Yb:fibre laser system readily scaled the usable pump energy. This was combined with a technique known as cavity-length extension, which allows a lowering of the cavity roundtrip time offering the build-up of pulses with increased energy. In a final stage, cavity-dumping on basis of an acousto-optic modulator was introduced into the a redesigned cavity. The combination of these three techniques, novel to synchronously pumped optical parametric oscillators, enabled the extraction of record-high pulse energies and peak power
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
Development of high reliability, high frequency power conditioning models of converter regulators
High efficiency conversion, regulation, and filtering techniques are discussed for power using high conversion frequencies; i.e., in the order of 1 to 5 MHz for converters having total output power capability in the order of 20 watts and 200 to 500 KHz for converters having total output powers in excess of 200 watts. Work centered on areas of component selection, material selection, optimization of the various types of circuits required, and the selection of materials for and design of magnetic components. These techniques were then applied to the design of two sample converters, one a medium power instrument type converter and the second a high power converter representative of a primary spacecraft converter regulator. The configuration and performance of the two converters is reported and discussed
Design And Implementation Of Up-Conversion Mixer And Lc-Quadrature Oscillator For IEEE 802.11a WLAN Transmitter Application Utilizing 0.18 Pm CMOS Technology [TK7871.99.M44 H279 2008 f rb].
Perlumbaan implementasi litar terkamil radio, dengan kos yang rendah telah menggalakkan penggunaan teknologi CMOS.
The drive for cost reduction has led to the use of CMOS technology for highly integrated radios
Solid-state-biased coherent detection of ultra-broadband terahertz pulses
Significant progress in nonlinear and ultrafast optics has recently opened new and exciting opportunities for terahertz (THz) science and technology, which require the development of reliable THz sources, detectors, and supporting devices. In this work, we demonstrate the first solid-state technique for the coherent detection of ultra-broadband THz pulses (0.1–10 THz), relying on the electric-field-induced second-harmonic generation in a thin layer of ultraviolet fused silica. The proposed CMOS-compatible devices, which can be realized with standard microfabrication techniques, allow us to perform ultra-broadband detection with a high dynamic range by employing probe laser powers and bias voltages much lower than those used in gas-based techniques. Eventually, this may pave the way for the use of high-repetition-rate ultrafast lasers and commercially available electronics for the coherent detection of ultrashort THz pulses
NASA Tech Briefs Index, 1977, volume 2, numbers 1-4
Announcements of new technology derived from the research and development activities of NASA are presented. Abstracts, and indexes for subject, personal author, originating center, and Tech Brief number are presented for 1977
Index to NASA Tech Briefs, 1975
This index contains abstracts and four indexes--subject, personal author, originating Center, and Tech Brief number--for 1975 Tech Briefs
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