The Experts below are selected from a list of 135 Experts worldwide ranked by ideXlab platform
Yoshihisa Yamamoto - One of the best experts on this subject based on the ideXlab platform.
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complete quantum control of a single quantum dot spin using ultrafast optical pulses
Nature, 2008Co-Authors: David Press, Thaddeus D Ladd, Bingyang Zhang, Yoshihisa YamamotoAbstract:A single electron spin confined within a semiconductor nanostructure is an ideal qubit for quantum computing, as it is relatively stable against decoherence and is easily manipulated electrically or optically. Full quantum control involving initialization, spin rotation and detection, has been demonstrated previously using electrically controlled radio-frequency pulses, but this method will be too slow for the construction of quantum computing circuits operating at useful clock speeds. Optical manipulation of electron spin allows much faster operations and has the added advantage that it allows for an optical interface. Press et al. now achieve ultrafast optical control of electron spin in a quantum dot and demonstrate, in combination with optical initialization and detection, a single-qubit logic gate operation, involving a sequence of two optical pulses. Such high-speed operation could conceivably lead to quantum computing devices at gigahertz clock speeds. A basic requirement for quantum information processing systems is the ability to completely control the state of a single qubit1,2,3,4,5,6. For qubits based on electron spin, a universal single-qubit gate is realized by a rotation of the spin by any angle about an Arbitrary Axis. Driven, coherent Rabi oscillations between two spin states can be used to demonstrate control of the rotation angle. Ramsey interference, produced by two coherent spin rotations separated by a variable time delay, demonstrates control over the Axis of rotation. Full quantum control of an electron spin in a quantum dot has previously been demonstrated using resonant radio-frequency pulses that require many spin precession periods7,8,9,10. However, optical manipulation of the spin allows quantum control on a picosecond or femtosecond timescale11,12,13,14,15,16,17,18, permitting an Arbitrary rotation to be completed within one spin precession period6. Recent work in optical single-spin control has demonstrated the initialization of a spin state in a quantum dot19,20,21,22, as well as the ultrafast manipulation of coherence in a largely unpolarized single-spin state17. Here we demonstrate complete coherent control over an initialized electron spin state in a quantum dot using picosecond optical pulses. First we vary the intensity of a single optical pulse to observe over six Rabi oscillations between the two spin states; then we apply two sequential pulses to observe high-contrast Ramsey interference. Such a two-pulse sequence realizes an Arbitrary single-qubit gate completed on a picosecond timescale. Along with the spin initialization and final projective measurement of the spin state, these results demonstrate a complete set of all-optical single-qubit operations.
James Friend - One of the best experts on this subject based on the ideXlab platform.
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surface acoustic wave micromotor with Arbitrary Axis rotational capability
Applied Physics Letters, 2011Co-Authors: Ricky T. Tjeung, Mark S. Hughes, Leslie Y Yeo, James FriendAbstract:A surface acoustic wave (SAW) actuated rotary motor is reported here, consisting of a millimeter-sized spherical metal rotor placed on the surface of a lead zirconate titanate piezoelectric substrate upon which the SAW is made to propagate. At the design frequency of 3.2 MHz and with a fixed preload of 41.1 μN, the maximum rotational speed and torque achieved were approximately 1900 rpm and 5.37 μN-mm, respectively, producing a maximum output power of 1.19 μW. The surface vibrations were visualized using laser Doppler vibrometry and indicate that the rotational motion arises due to retrograde elliptical motions of the piezoelectric surface elements. Rotation about orthogonal axes in the plane of the substrate has been obtained by using orthogonally placed interdigital electrodes on the substrate to generate SAW impinging on the rotor, offering a means to generate rotation about an Arbitrary Axis in the plane of the substrate.
Ricky T. Tjeung - One of the best experts on this subject based on the ideXlab platform.
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surface acoustic wave micromotor with Arbitrary Axis rotational capability
Applied Physics Letters, 2011Co-Authors: Ricky T. Tjeung, Mark S. Hughes, Leslie Y Yeo, James FriendAbstract:A surface acoustic wave (SAW) actuated rotary motor is reported here, consisting of a millimeter-sized spherical metal rotor placed on the surface of a lead zirconate titanate piezoelectric substrate upon which the SAW is made to propagate. At the design frequency of 3.2 MHz and with a fixed preload of 41.1 μN, the maximum rotational speed and torque achieved were approximately 1900 rpm and 5.37 μN-mm, respectively, producing a maximum output power of 1.19 μW. The surface vibrations were visualized using laser Doppler vibrometry and indicate that the rotational motion arises due to retrograde elliptical motions of the piezoelectric surface elements. Rotation about orthogonal axes in the plane of the substrate has been obtained by using orthogonally placed interdigital electrodes on the substrate to generate SAW impinging on the rotor, offering a means to generate rotation about an Arbitrary Axis in the plane of the substrate.
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Arbitrary Axis rotating surface acoustic wave micro motor
2011 6th IEEE International Conference on Nano Micro Engineered and Molecular Systems, 2011Co-Authors: Ricky T. Tjeung, Mark S. Hughes, James R. FriendAbstract:We present a surface acoustic wave (SAW) actuated rotating micro motor. The rotors are 1 millimeter metal spheres which are placed on the surface of a Lead Zirconate Titanate (PZT) substrate with IDTs designed to generate SAW with ~ 700 μm wavelength. A Laser Doppler Vibrometer (LDV) was used to visualize the travelling SAW and the result was compared with the rotation of the rotor. The motor transient responses are presented, along with its torque-speed curve. The maximum rotational speed and torque reported were ~1000 rpm and ~14 μN.mm, respectively. Arbitrary motions have also been demonstrated utilizing a magnetic pre-load and multiple IDTs activation.
Charles Watson - One of the best experts on this subject based on the ideXlab platform.
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a multidimensional magnetic resonance histology atlas of the wistar rat brain
NeuroImage, 2012Co-Authors: Allan G Johnson, Evan Calabrese, Alexandra Badea, George Paxinos, Charles WatsonAbstract:We have produced a multidimensional atlas of the adult Wistar rat brain based on magnetic resonance histology (MRH). This MR atlas has been carefully aligned with the widely used Paxinos-Watson atlas based on optical sections to allow comparisons between histochemical and immuno-marker data, and the use of the Paxinos-Watson abbreviation set. Our MR atlas attempts to make a seamless connection with the advantageous features of the Paxinos-Watson atlas, and to extend the utility of the data through the unique capabilities of MR histology: a) ability to view the brain in the skull with limited distortion from shrinkage or sectioning; b) isotropic spatial resolution, which permits sectioning along any Arbitrary Axis without loss of detail; c) three-dimensional (3D) images preserving spatial relationships; and d) widely varied contrast dependent on the unique properties of water protons. 3D diffusion tensor images (DTI) at what we believe to be the highest resolution ever attained in the rat provide unique insight into white matter structures and connectivity. The 3D isotropic data allow registration of multiple data sets into a common reference space to provide average atlases not possible with conventional histology. The resulting multidimensional atlas that combines Paxinos-Watson with multidimensional MRH images from multiple specimens provides a new, comprehensive view of the neuroanatomy of the rat and offers a collaborative platform for future rat brain studies.
Mark S. Hughes - One of the best experts on this subject based on the ideXlab platform.
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surface acoustic wave micromotor with Arbitrary Axis rotational capability
Applied Physics Letters, 2011Co-Authors: Ricky T. Tjeung, Mark S. Hughes, Leslie Y Yeo, James FriendAbstract:A surface acoustic wave (SAW) actuated rotary motor is reported here, consisting of a millimeter-sized spherical metal rotor placed on the surface of a lead zirconate titanate piezoelectric substrate upon which the SAW is made to propagate. At the design frequency of 3.2 MHz and with a fixed preload of 41.1 μN, the maximum rotational speed and torque achieved were approximately 1900 rpm and 5.37 μN-mm, respectively, producing a maximum output power of 1.19 μW. The surface vibrations were visualized using laser Doppler vibrometry and indicate that the rotational motion arises due to retrograde elliptical motions of the piezoelectric surface elements. Rotation about orthogonal axes in the plane of the substrate has been obtained by using orthogonally placed interdigital electrodes on the substrate to generate SAW impinging on the rotor, offering a means to generate rotation about an Arbitrary Axis in the plane of the substrate.
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Arbitrary Axis rotating surface acoustic wave micro motor
2011 6th IEEE International Conference on Nano Micro Engineered and Molecular Systems, 2011Co-Authors: Ricky T. Tjeung, Mark S. Hughes, James R. FriendAbstract:We present a surface acoustic wave (SAW) actuated rotating micro motor. The rotors are 1 millimeter metal spheres which are placed on the surface of a Lead Zirconate Titanate (PZT) substrate with IDTs designed to generate SAW with ~ 700 μm wavelength. A Laser Doppler Vibrometer (LDV) was used to visualize the travelling SAW and the result was compared with the rotation of the rotor. The motor transient responses are presented, along with its torque-speed curve. The maximum rotational speed and torque reported were ~1000 rpm and ~14 μN.mm, respectively. Arbitrary motions have also been demonstrated utilizing a magnetic pre-load and multiple IDTs activation.