218,465 research outputs found
Quantum-measurement backaction from a Bose-Einstein condensate coupled to a mechanical oscillator
We study theoretically the dynamics of a hybrid optomechanical system consisting of a macroscopic mechanical membrane magnetically coupled to a spinor Bose-Einstein condensate via a nanomagnet attached at the membrane center. We demonstrate that this coupling permits us to monitor indirectly the center-of-mass position of the membrane via measurements of the spin of the condensed atoms. These measurements normally induce a significant backaction on the membrane motion, which we quantify for the cases of thermal and coherent initial states of the membrane. We discuss the possibility of measuring this quantum backaction via repeated measurements. We also investigate the potential to generate nonclassical states of the membrane, in particular Schrödinger-cat states, via such repeated measurements
H1 photonic crystal cavitites for hybrid quantum information protocols
Hybrid quantum information protocols are based on local qubits, such as
trapped atoms, NV centers, and quantum dots, coupled to photons. The coupling
is achieved through optical cavities. Here we demonstrate far-field optimized
H1 photonic crystal membrane cavities combined with an additional back
reflection mirror below the membrane that meet the optical requirements for
implementing hybrid quantum information protocols. Using numerical optimization
we find that 80% of the light can be radiated within an objective numerical
aperture of 0.8, and the coupling to a single-mode fiber can be as high as 92%.
We experimentally prove the unique external mode matching properties by
resonant reflection spectroscopy with a cavity mode visibility above 50%.Comment: 14 pages, 11 figure
Quantum measurement backaction from a BEC coupled to a mechanical oscillator
We study theoretically the dynamics of a a hybrid optomechanical system
consisting of a macroscopic mechanical membrane magnetically coupled to a
spinor Bose-Einstein condensate via a nanomagnet attached at the membrane
center. We demonstrate that this coupling permits us to monitor indirectly the
center-of-mass position of the membrane via measurements of the spin of the
condensed atoms. These measurements normally induce a significant backaction on
the membrane motion, which we quantify for the cases of thermal and coherent
initial states of the membrane. We discuss the possibility of measuring that
quantum backaction via repeated measurements. We also investigate the potential
to generate non-classical states of the membrane, in particular Schrodinger cat
states, via such repeated measurements.Comment: 14 pages, 4 figures. Submitted to PR
Import of honeybee prepromelittin into the endoplasmic reticulum
Honeybee prepromelittin is correctly processed and imported by dog pancreas microsomes. Insertion of prepromelittin into microsomal membranes, as assayed by signal sequence removal, does not depend on signal recognition particle (SRP) and docking protein. We addressed the question as to how prepromelittin bypasses the SRP/docking protein system. Hybrid proteins between prepromelittin, or carboxy-terminally truncated derivatives, and the cytoplasmic protein dihydrofolate reductase from mouse were constructed. These hybrid proteins were analysed for membrane insertion and sequestration into microsomes. The results suggest the following: (i) The signal sequence of prepromelittin is capable of interacting with the SRP/docking protein system, but this interaction is not mandatory for membrane insertion; this is related to the small size of prepromelittin. (ii) In prepromelittin a cluster of negatively charged amino acids must be balanced by a cluster of positively charged amino acids in order to allow membrane insertion. (iii) In general, a signal sequence can be sufficient to mediate membrane insertion independently of SRP and docking protein in the case of short precursor proteins; however, the presence and distribution of charged amino acids within the mature part of these precursors can play distinct roles
Effect of periodic backwash in the submerged membrane adsorption hybrid system
The submerged membrane adsorption hybrid system (SMAHS) is an attractive solution in treating wastewater; however it faces membrane fouling although to a less extent. In this study, different adsorbents and resins were investigated in order to find a substitute to the powdered activated carbon (PAC); The effect of new backflush was also studied in further reducing the membrane fouling. The SMAHS led to 72–86% dissolved organic carbon (DOC) removal. A detailed study on the transmembrane pressure development led to a conclusion that there is a critical flux and this value is around 16 l/h.m2 for the wastewater studied
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