2,102 research outputs found
Principles of Control for Decoherence-Free Subsystems
Decoherence-Free Subsystems (DFS) are a powerful means of protecting quantum
information against noise with known symmetry properties. Although Hamiltonians
theoretically exist that can implement a universal set of logic gates on DFS
encoded qubits without ever leaving the protected subsystem, the natural
Hamiltonians that are available in specific implementations do not necessarily
have this property. Here we describe some of the principles that can be used in
such cases to operate on encoded qubits without losing the protection offered
by the DFS. In particular, we show how dynamical decoupling can be used to
control decoherence during the unavoidable excursions outside of the DFS. By
means of cumulant expansions, we show how the fidelity of quantum gates
implemented by this method on a simple two-physical-qubit DFS depends on the
correlation time of the noise responsible for decoherence. We further show by
means of numerical simulations how our previously introduced "strongly
modulating pulses" for NMR quantum information processing can permit
high-fidelity operations on multiple DFS encoded qubits in practice, provided
that the rate at which the system can be modulated is fast compared to the
correlation time of the noise. The principles thereby illustrated are expected
to be broadly applicable to many implementations of quantum information
processors based on DFS encoded qubits.Comment: 12 pages, 7 figure
Quantum Simulations on a Quantum Computer
We present a general scheme for performing a simulation of the dynamics of
one quantum system using another. This scheme is used to experimentally
simulate the dynamics of truncated quantum harmonic and anharmonic oscillators
using nuclear magnetic resonance. We believe this to be the first explicit
physical realization of such a simulation.Comment: 4 pages, 2 figures (\documentstyle[prl,aps,epsfig,amscd]{revtex}); to
appear in Phys. Rev. Let
Pengaruh Ion Pb(Ii) dan Ion Cd(Ii) terhadap Efektivitas Fotoreduksi Ion Hg(Ii) yang Terkatalisis Tio2
Pada penelitian ini telah dipelajari pengaruh ion Pb(II) dan Cd(II) pada konsentrasi terhadap efektivitas fotoreduksi ion Hg(II) yang terkatalisis TiO2. Proses fotoreduksi dilakukan dengan menyinari campuran yang terdiri dari larutan ion Hg(II) dan serbuk fotokatalis TiO2 dengan dan tanpa adanya ion Pb(II) maupun ion Cd(II), dalam reaktor yang dilengkapi dengan lampu UV. Kondisi proses fotoreduksi adalah 50 mL larutan ion Hg(II) 5 ppm, ion Pb(II) dan Cd(II) dengan konsentrasi yang bervariasi, TiO2 seberat 15 mg, pH larutan 4 dan waktu reaksi selama 24 jam. Jumlah Hg(II) yang tereduksi dihitung berdasarkan selisih antara konsentrasi ion Hg(II) awal dengan konsentrasi ion Hg(II) sisa dalam larutan setelah proses fotoreduksi. Konsentrasi Hg(II) sisa ditentukan dengan metode Spektrofotometri Serapan Atom teknik pembangkit uap dingin atau Cold Vapor Atomic Absorption Spectrophotometric method (CV-AAS). Hasil penelitian menunjukkan efektivitas fotoreduksi ion Hg(II) terkatalisis TiO2 dengan adanya ion Pb(II) mengalami peningkatan seiring dengan kenaikan konsentrasi ion Pb(II) yaitu dari 80,8% menjadi 98,92%, hal ini terjadi karena adanya efek sinergi. Sebaliknya fotoreduksi ion Hg(II) dengan adanya penambahan ion Cd(II) dengan konsentrasi yang semakin besar menjadi berkurang yaitu dari 80,8% menjadi 33,32% disebabkan terjadi kompetisi adsorpsi
Multi-spin dynamics of the solid-state NMR Free Induction Decay
We present a new experimental investigation of the NMR free induction decay
(FID) in a lattice of spin-1/2 nuclei in a strong Zeeman field. Following a
pi/2 pulse, evolution under the secular dipolar Hamiltonian preserves coherence
number in the Zeeman eigenbasis, but changes the number of correlated spins in
the state. The observed signal is seen to decay as single-spin, single-quantum
coherences evolve into multiple-spin coherences under the action of the dipolar
Hamiltonian. In order to probe the multiple-spin dynamics during the FID, we
measured the growth of coherence orders in a basis other than the usual Zeeman
eigenbasis. This measurement provides the first direct experimental observation
of the growth of coherent multiple-spin correlations during the FID.
Experiments were performed with a cubic lattice of spins (19F in calcium
fluoride) and a linear spin chain (19F in fluorapatite). It is seen that the
geometrical arrangement of the spins plays a significant role in the
development of higher order correlations. The results are discussed in light of
existing theoretical models.Comment: 7 pages, 6 figure
Implement Smart Sensors With Wireless Communication Protocols With Embedded Microcontrollers in a Capstone Project Design
Wireless communication has become popular and widely used in our daily lives. Their applications are: Cellular Wireless for telephone systems, data collection, voice communication, and other mobile or extremely remote devices, Bluetooth for low-power applications in short range and moderate date bandwidth, Proprietary ISM (industrial, scientific, medical) protocols used in open frequency bands from 260 to 470 MHz, 902 to 928 MHz, and 2.4GHz, 802.11/WiFi in wireless data communications, 802.15/ZigBee for mesh networks of sensors and controllers, and Z-Wave for low speed wireless protocol of home electronics devices to intercommunicate using reliable protocol that easily travels through walls, floors, and cabinets1.
Sensors with embedded intelligence and integrated with cost effective wireless protocols have been recognized as smart sensors in many applications, such as smart home appliances, home automation, green technology in energy conservation and harvesting, and remote data logging etc2. This application project is implemented in the classification between Proprietary ISM, ZigBee, and Z-Wave wireless applications. It is built based on the MRF24J40MA (2.4GHz RF modules) that follows the IEEE 802.15.4TM-2003 rules7, standards, and software protocols designs with SPI (Serial Peripheral Interface)9 interfacing to a PIC16F877A microcontroller. The project uses three 2.4 GHz RF modules (MRF24J40MA), and three PIC16F877A units hosted in three previously developed low cost PIC microcontroller training systems3. The sensor stations are designed as Slave units and responsible for conditioning and reporting temperature, humidity, and atmospheric pressure. The control unit is categorized as a Master station and responsible for interacting with user/host to decide when, where, and how to report the data to the inquiries. In addition to sensors on the Slaves station, there are assistances from real time clock and external serial EEPROM devices to provide time stamped real time data for future inquiry from the Master. All the communications between the Master and multiple Slaves are through wireless RF signals with customized software protocol designs4
Experimental Implementation of Logical Bell State Encoding
Liquid phase NMR is a general purpose test-bed for developing methods of
coherent control relevant to quantum information processing. Here we extend
these studies to the coherent control of logical qubits and in particular to
the unitary gates necessary to create entanglement between logical qubits. We
report an experimental implementation of a conditional logical gate between two
logical qubits that are each in decoherence free subspaces that protect the
quantum information from fully correlated dephasing.Comment: 9 Pages, 5 Figure
Quantitative assay for farnesol and the aromatic fusel alcohols from the fungus \u3ci\u3eCandida albicans\u3c/i\u3e
The dimorphic fungus Candida albicans is a commensal and opportunistic fungal pathogen of humans. It secretes at least four small lipophilic molecules, farnesol and three aromatic fusel alcohols. Farnesol has been identified as both a quorum sensing molecule (QSM) and a virulence factor. Our gas chromatography (GC)-based assay for these molecules exhibits high throughput, prevention of analyte loss by avoiding filtration and rotary evaporation, simultaneous cell lysis and analyte extraction by ethyl acetate, and the ability to compare whole cultures with their cell pellets and supernatants. Farnesol synthesis and secretion were separable phenomena and pellet:supernatant ratios for farnesol were high, up to 12:1. The assay was validated in terms of precision, specificity, ruggedness, accuracy, solution stability, detection limits (DL), quantitation limits (QL), and dynamic range. The DL for farnesol was 0.02 ng/μl (0.09 μM). Measurement quality was assessed by the relative error of the whole culture versus the sum of pellet and supernatant fractions (WPS). C. albicans strain SC5314 grown at 30 °C in complex and defined media (YPD and mRPMI) was assayed in biological triplicate 17 times over 3 days. Farnesol and the three aromatic fusel alcohols can be measured in the same assay. The levels of all four are greatly altered by the growth medium chosen. Significantly, the three fusel alcohols are synthesized during stationary phase, not during growth. They are secreted quickly without being retained in the cell pellet and may accumulate up to mM concentrations
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