The Experts below are selected from a list of 3504 Experts worldwide ranked by ideXlab platform
Dieter Suter - One of the best experts on this subject based on the ideXlab platform.
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Bloch-Siegert shift in a hybrid Quantum Register: Quantification and compensation
Physical Review A, 2018Co-Authors: Jingfu Zhang, Sagnik Saha, Dieter SuterAbstract:Quantum information processing relies on unitary transformations applied to specific qubits. In most cases, these gate operations are driven by alternating electromagnetic fields that are near resonant with specific transitions between eigenstates of the system Hamiltonian. For single-qubit gate operations, they should implement the operation on the target qubit, while all other qubits should be left invariant. It is typically assumed that this goal can be achieved if the amplitude of the control field is small compared to the frequency difference between the field and the transition frequency of the passive qubits. However, in many cases, even qubits whose energy-level differences are very far from the frequency of the applied control field can be affected by nonresonant effects, which are normally nonlinear in the amplitude of the control field. A typical example is the effect known as Bloch-Siegert shift. Unless these shifts are accounted for and, if possible, compensated, they can completely destroy the information contained in the Quantum Register. Therefore, we study this effect quantitatively in the important example of the nitrogen vacancy center in diamond and demonstrate how it can be eliminated.
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Pulse sequences for controlled two- and three-qubit gates in a hybrid Quantum Register
Physical Review A, 2018Co-Authors: Jingfu Zhang, Swathi S. Hegde, Dieter SuterAbstract:We propose and demonstrate a Quantum control scheme for hybrid Quantum Registers that can reduce the operation time, and therefore the effects of relaxation, compared to existing implementations. It combines resonant excitation pulses with periods of free precession under the internal Hamiltonian of the qubit system. We use this scheme to implement Quantum gates like controlled-NOT operations on electronic and nuclear spins of the nitrogen-vacancy center in diamond. As a specific application, we transfer population between electronic and nuclear spin qubits and use it to measure the Rabi oscillations of a nuclear spin in a system with multiple coupled spins.
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Decoherence in large Quantum Registers under variable interaction with the environment
Physical Review A, 2007Co-Authors: Marko Lovrić, Hans Georg Krojanski, Dieter SuterAbstract:Effective Quantum-information processing requires coherent control of large numbers of qubits on a time scale that is short compared to the decoherence time of the system. It is therefore important to extrapolate and measure decoherence times for large Quantum Registers and to determine the effect of different couplings between system and environment on the decoherence rate. For this purpose, we have experimentally realized a system that allows one to generate model Quantum Registers with more than 100 qubits and measure the decay of the information in these states while adjusting the strength of the interaction between the Quantum Register and the environment. Our results indicate a power-law dependence of the decoherence rate on the number of qubits in the system, with an exponent of the order of 0.5. This behavior remains qualitatively unchanged when the coupling strength to the environment is reduced by about an order of magnitude.
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Reduced Decoherence in Large Quantum Registers
Physical review letters, 2006Co-Authors: Hans Georg Krojanski, Dieter SuterAbstract:Among the biggest obstacles for building larger (and thus more powerful) Quantum-information processors is decoherence, the decay of Quantum-information by the coupling between the Quantum Register and its environment. Procedures for reducing decoherence processes will be essential for successful operation of larger Quantum processors. We study model Quantum Registers consisting of up to 4900 qubits and measure their decay as a function of the Register size. We demonstrate that appropriate sequences of qubit rotations reduce the coupling between system and environment for all sizes of the Quantum Register, thus preserving the Quantum-information 50 times longer than without decoupling.
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Scaling of decoherence in wide NMR Quantum Registers.
Physical review letters, 2004Co-Authors: Hans Georg Krojanski, Dieter SuterAbstract:Among the most important parameters for the usefulness of Quantum computers are the size of the Quantum Register and the decoherence time for the Quantum information. The decoherence time is expected to get shorter with the number of correlated qubits, but experimental data are only available for small numbers of qubits. Solid-state nuclear magnetic resonance allows one to correlate large numbers of qubits (several hundred) and measure their decoherence rates. We use a modified magnetic dipole-dipole interaction to correlate the proton spins in a solid sample and observe the decay of the resulting highly correlated states. By systematically varying the number of correlated spins, we measure the increase of the decoherence rate with the size of the Quantum Register.
Kareljan Schoutens - One of the best experts on this subject based on the ideXlab platform.
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Spin texture readout of a moore-read topological Quantum Register.
Physical review letters, 2012Co-Authors: J.c. Romers, Kareljan SchoutensAbstract:We study the composite charged spin texture (CST) over the Moore-Read Quantum Hall state that arises when a collection of elementary CSTs is moved to the same location. Following an algebraic approach based on the characteristic pair correlations of the Moore-Read state, we find that the spin texture associated with a composite CST is set by the fusion sector of the underlying non-Abelian quasiparticles. This phenomenon provides a novel way to read out the Quantum Register of a non-Abelian topologically ordered phase.
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Wavefunctions for topological Quantum Registers
Annals of Physics, 2007Co-Authors: Eddy Ardonne, Kareljan SchoutensAbstract:Abstract We present explicit wavefunctions for quasi-hole excitations over a variety of non-abelian Quantum Hall states: the Read–Rezayi states with k ⩾ 3 clustering properties and a paired spin-singlet Quantum Hall state. Quasi-holes over these states constitute a topological Quantum Register, which can be addressed by braiding quasi-holes. We obtain the braid properties by direct inspection of the quasi-hole wavefunctions. We establish that the braid properties for the paired spin-singlet state are those of ‘Fibonacci anyons’, and thus suitable for universal Quantum computation. Our derivations in this paper rely on explicit computations in the parafermionic conformal field theories that underly these particular Quantum Hall states.
Armando Rastelli - One of the best experts on this subject based on the ideXlab platform.
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Nuclear spin Quantum Register in an optically active semiconductor Quantum dot
Nature Nanotechnology, 2020Co-Authors: Evgeny A. Chekhovich, Saimon F. Covre Silva, Armando RastelliAbstract:Epitaxial Quantum dots (QDs) have long been identified as promising charge spin qubits offering an efficient interface to Quantum light and advanced semiconductor nanofabrication technologies. However, charge spin coherence is limited by interaction with the nanoscale ensemble of atomic nuclear spins, which is particularly problematic in strained self-assembled dots. Here, we use strain-free GaAs/AlGaAs QDs, demonstrating a fully functioning two-qubit Quantum Register using the nanoscale ensemble of arsenic quadrupolar nuclear spins as its hardware. Tailored radio-frequency pulses allow Quantum state storage for up to 20 ms, and are used for few-microsecond single-qubit and two-qubit control gates with fidelities exceeding 97%. Combining long coherence and high-fidelity control with optical initialization and readout, we implement benchmark Quantum computations such as Grover’s search and the Deutsch–Jozsa algorithm. Our results identify QD nuclei as a potential Quantum information resource, which can complement charge spins and light particles in future QD circuits. Epitaxial Quantum dot charge spin qubits offer efficient Quantum light links, but their coherence is limited by interactions with the nanoscale ensemble of atomic nuclear spins. Employing nuclear spins instead as its hardware, strain-free GaAs/AlGaAs Quantum dots can constitute a fully functional two-qubit Quantum Register.
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Nuclear spin Quantum Register in an optically active semiconductor Quantum dot.
Nature nanotechnology, 2020Co-Authors: Evgeny A. Chekhovich, Saimon F. Covre Silva, Armando RastelliAbstract:Epitaxial Quantum dots (QDs) have long been identified as promising charge spin qubits offering an efficient interface to Quantum light and advanced semiconductor nanofabrication technologies. However, charge spin coherence is limited by interaction with the nanoscale ensemble of atomic nuclear spins, which is particularly problematic in strained self-assembled dots. Here, we use strain-free GaAs/AlGaAs QDs, demonstrating a fully functioning two-qubit Quantum Register using the nanoscale ensemble of arsenic quadrupolar nuclear spins as its hardware. Tailored radio-frequency pulses allow Quantum state storage for up to 20 ms, and are used for few-microsecond single-qubit and two-qubit control gates with fidelities exceeding 97%. Combining long coherence and high-fidelity control with optical initialization and readout, we implement benchmark Quantum computations such as Grover's search and the Deutsch-Jozsa algorithm. Our results identify QD nuclei as a potential Quantum information resource, which can complement charge spins and light particles in future QD circuits.
Philipp Neumann - One of the best experts on this subject based on the ideXlab platform.
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measuring broadband magnetic fields on the nanoscale using a hybrid Quantum Register
Nature Nanotechnology, 2017Co-Authors: Ingmar Jakobi, Philipp Neumann, Matthew Markham, Ya Wang, Durga Bhaktavatsala Rao Dasari, Fadi El Hallak, M A Bashir, Andrew M Edmonds, D J TwitchenAbstract:The precise characterization of magnetic fields with a bandwidth of up to 3 GHz and localized on a nanometric scale is achieved by means of the coherent control of single electron and nuclear spins.
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Quantum simulation of helium hydride cation in a solid state spin Register
ACS Nano, 2015Co-Authors: Ya Wang, Philipp Neumann, Ingmar Jakobi, Florian Dolde, Jacob Biamonte, Ryan Babbush, Ville Bergholm, Sen Yang, Alan Aspuruguzik, James D WhitfieldAbstract:Ab initio computation of molecular properties is one of the most promising applications of Quantum computing. While this problem is widely believed to be intractable for classical computers, efficient Quantum algorithms exist which have the potential to vastly accelerate research throughput in fields ranging from material science to drug discovery. Using a solid-state Quantum Register realized in a nitrogen-vacancy (NV) defect in diamond, we compute the bond dissociation curve of the minimal basis helium hydride cation, HeH+. Moreover, we report an energy uncertainty (given our model basis) of the order of 10–14 hartree, which is 10 orders of magnitude below the desired chemical precision. As NV centers in diamond provide a robust and straightforward platform for Quantum information processing, our work provides an important step toward a fully scalable solid-state implementation of a Quantum chemistry simulator.
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Quantum Register based on coupled electron spins in a room temperature solid
Nature Physics, 2010Co-Authors: Philipp Neumann, Florian Rempp, Roman Kolesov, Boris Naydenov, J Beck, Matthias Steiner, V Jacques, Gopalakrishnan Balasubramanian, Matthew Markham, D J TwitchenAbstract:Nitrogen–vacancy centres in diamond have emerged as a promising platform for Quantum information processing at room temperature. Now, coherent coupling between two electron spins separated by almost 10 nm has been demonstrated. At this distance, the spins can be addressed individually, which might enable the construction of a network of connected Quantum Registers.
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Multipartite entanglement among single spins in diamond
Science, 2008Co-Authors: Philipp Neumann, Florian Rempp, Vairon Jacques, Norikazu Mizuochi, S Yamasaki, H. Watanabe, Vincent JacquesAbstract:Robust entanglement at room temperature is a necessary requirement for practical applications in Quantum technology. We demonstrate the creation of bipartite- and tripartite-entangled Quantum states in a small Quantum Register consisting of individual 13C nuclei in a diamond lattice. Individual nuclear spins are controlled via their hyperfine coupling to a single electron at a nitrogen-vacancy defect center. Quantum correlations are of high quality and persist on a millisecond time scale even at room temperature, which is adequate for sophisticated Quantum operations.
Evgeny A. Chekhovich - One of the best experts on this subject based on the ideXlab platform.
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Nuclear spin Quantum Register in an optically active semiconductor Quantum dot
Nature Nanotechnology, 2020Co-Authors: Evgeny A. Chekhovich, Saimon F. Covre Silva, Armando RastelliAbstract:Epitaxial Quantum dots (QDs) have long been identified as promising charge spin qubits offering an efficient interface to Quantum light and advanced semiconductor nanofabrication technologies. However, charge spin coherence is limited by interaction with the nanoscale ensemble of atomic nuclear spins, which is particularly problematic in strained self-assembled dots. Here, we use strain-free GaAs/AlGaAs QDs, demonstrating a fully functioning two-qubit Quantum Register using the nanoscale ensemble of arsenic quadrupolar nuclear spins as its hardware. Tailored radio-frequency pulses allow Quantum state storage for up to 20 ms, and are used for few-microsecond single-qubit and two-qubit control gates with fidelities exceeding 97%. Combining long coherence and high-fidelity control with optical initialization and readout, we implement benchmark Quantum computations such as Grover’s search and the Deutsch–Jozsa algorithm. Our results identify QD nuclei as a potential Quantum information resource, which can complement charge spins and light particles in future QD circuits. Epitaxial Quantum dot charge spin qubits offer efficient Quantum light links, but their coherence is limited by interactions with the nanoscale ensemble of atomic nuclear spins. Employing nuclear spins instead as its hardware, strain-free GaAs/AlGaAs Quantum dots can constitute a fully functional two-qubit Quantum Register.
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Nuclear spin Quantum Register in an optically active semiconductor Quantum dot.
Nature nanotechnology, 2020Co-Authors: Evgeny A. Chekhovich, Saimon F. Covre Silva, Armando RastelliAbstract:Epitaxial Quantum dots (QDs) have long been identified as promising charge spin qubits offering an efficient interface to Quantum light and advanced semiconductor nanofabrication technologies. However, charge spin coherence is limited by interaction with the nanoscale ensemble of atomic nuclear spins, which is particularly problematic in strained self-assembled dots. Here, we use strain-free GaAs/AlGaAs QDs, demonstrating a fully functioning two-qubit Quantum Register using the nanoscale ensemble of arsenic quadrupolar nuclear spins as its hardware. Tailored radio-frequency pulses allow Quantum state storage for up to 20 ms, and are used for few-microsecond single-qubit and two-qubit control gates with fidelities exceeding 97%. Combining long coherence and high-fidelity control with optical initialization and readout, we implement benchmark Quantum computations such as Grover's search and the Deutsch-Jozsa algorithm. Our results identify QD nuclei as a potential Quantum information resource, which can complement charge spins and light particles in future QD circuits.