scholarly journals Isotopically enhanced triple-quantum-dot qubit

2015 ◽  
Vol 1 (4) ◽  
pp. e1500214 ◽  
Author(s):  
Kevin Eng ◽  
Thaddeus D. Ladd ◽  
Aaron Smith ◽  
Matthew G. Borselli ◽  
Andrey A. Kiselev ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Coherent Control ◽  
Spin Echo ◽  
Pulse Sequences ◽  
Low Noise ◽  
Single Shot ◽  
Spin Qubit ◽  
Echo Type ◽  
Silicon Based ◽  
Long Pulse

Like modern microprocessors today, future processors of quantum information may be implemented using all-electrical control of silicon-based devices. A semiconductor spin qubit may be controlled without the use of magnetic fields by using three electrons in three tunnel-coupled quantum dots. Triple dots have previously been implemented in GaAs, but this material suffers from intrinsic nuclear magnetic noise. Reduction of this noise is possible by fabricating devices using isotopically purified silicon. We demonstrate universal coherent control of a triple-quantum-dot qubit implemented in an isotopically enhanced Si/SiGe heterostructure. Composite pulses are used to implement spin-echo type sequences, and differential charge sensing enables single-shot state readout. These experiments demonstrate sufficient control with sufficiently low noise to enable the long pulse sequences required for exchange-only two-qubit logic and randomized benchmarking.

Rapid Lumbar Spine MR Myelography: Imaging Findings Using a Single-Shot Technique

1997 ◽  
Vol 10 (2) ◽  
pp. 181-187 ◽  
Author(s):  
P. Demaerel ◽  
P. Van Hover ◽  
A. Broeders ◽  
B. Kiefer ◽  
A.L. Baert
Keyword(s):  
Spin Echo ◽  
Pulse Sequences ◽  
Three Dimensional ◽  
Projection Algorithm ◽  
Fast Spin Echo ◽  
Single Shot ◽  
Rapid Acquisition ◽  
Spin Echo Sequence ◽  
Echo Pulse ◽  
Mr Myelography

MR myelography has been performed by several authors. Most authors have used techniques based on three-dimensional gradient-echo pulse sequences or fast spin-echo pulse sequences. The examination time varied between 5 and 13 minutes and postprocessing with a maximum-intensity projection algorithm was necessary for three-dimensional visualization. The rapid acquisition with relaxation enhancement (RARE) was initially described by Hennig et Al. In this technical note we present our experience with a single-shot turbo spin-echo sequence, derived from RARE, of approximately 2 seconds to obtain one view. MR myelography can replace conventional myelography in all different types of pathology. In addition MR myelography provides additional information compared to MR imaging in a minority of the cases. Taking into account the ultra-rapid acquisition and the absence of postprocessing procedures, we recommended this technique in the appropriate clinical setting. The MR myelogram increases the level of conficence of the neuroradiologist.

scholarly journals MRI of the lung: Value of different turbo spin-echo, single-shot turbo spin-echo, and 3D gradient-echo pulse sequences for the detection of pulmonary metastases

2007 ◽  
Vol 25 (1) ◽  
pp. 73-81 ◽  
Author(s):  
Melanie Bruegel ◽  
Jochen Gaa ◽  
Klaus Woertler ◽  
Carl Ganter ◽  
Simone Waldt ◽  
...  
Keyword(s):  
Pulmonary Metastases ◽  
Spin Echo ◽  
Pulse Sequences ◽  
Single Shot ◽  
Turbo Spin Echo ◽  
Gradient Echo ◽  
Turbo Spin ◽  
Echo Pulse

scholarly journals Electricgtensor control and spin echo of a hole-spin qubit in a quantum dot molecule

2010 ◽  
Vol 12 (9) ◽  
pp. 093012 ◽  
Author(s):  
Robert Roloff ◽  
Thomas Eissfeller ◽  
Peter Vogl ◽  
Walter Pötz
Keyword(s):  
Quantum Dot ◽  
Spin Echo ◽  
Spin Qubit

scholarly journals Age and gender dependence of liver diffusion parameters and the evidence of intravoxel incoherent motion modelling of perfusion component is constrained by diffusion component

2020 ◽  
Author(s):  
Hua Huang ◽  
Cun-Jing Zheng ◽  
Li-Fei Wang ◽  
Nazmi Che-Nordin ◽  
Yì Xiáng J. Wáng
Keyword(s):  
Spin Echo ◽  
Liver Perfusion ◽  
B Value ◽  
Single Shot ◽  
Age And Gender ◽  
Age Related ◽  
Diffusion Component ◽  
And Gender ◽  
Echo Type ◽  
Gender Dependence

AbstractObjectivesTo establish reference values for middle aged subjects and investigate age and gender dependence of liver diffusion MRI parameters.MethodsThe IVIM type of liver diffusion scan was based on a single-shot spin-echo type echo-planar sequence using a 1.5-T magnet with 16 b-values. DDVD (diffusion-derived vessel density) was the signal difference between b=0 and b=2 s/mm2 images after removing visible vessels. IVIM analysis was performed with full-fitting and segmented-fitting, and with threshold b-value of 60 or 200 s/mm2, and fitting started from b=2 s/mm2. 32 men (age range: 25-71 years) and 26 men (age: 22-69 years) had DDVD and IVIM analysis respectively, while 36 women (age: 20-71 years) had DDVD and IVIM analysis.ResultsDDVD had an age-related reduction noted for women. IVIM results of full fitting had good agreement with segmented fitting with threshold b of 60 s/mm2 results, but less so with results of threshold b of 200 s/mm2. As age increases, female subjects’ Dslow measure had significant reduction, and PF and Dfast measure had significant increase. For the age group of 40-55 years, DDVD, Dslow, PF, and Dfast were 12.27±3.90, 1.072±0.067 (10−3mm2/s), 0.141±0.025, 61.0±14.0 (10−3mm2/s), and 13.4±3.6, 1.069±0.074 mm2/s, 0.119±0.014, 57.1±13.2 mm2/s, for men and women, respectively.ConclusionDDVD measure suggest that aging may be associated with reduction in liver perfusion. Lower Dslow measurement can lead to artificial higher PF and Dfast measurement, providing the evidence of IVIM modeling of perfusion component is constrained by diffusion component.

scholarly journals Ultrafast coherent control of a hole spin qubit in a germanium quantum dot

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Ke Wang ◽  
Gang Xu ◽  
Fei Gao ◽  
He Liu ◽  
Rong-Long Ma ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Coherent Control ◽  
Coherence Time ◽  
Double Quantum ◽  
Spin Orbit ◽  
Spin Qubits ◽  
Single Spin ◽  
Operation Speed ◽  
Spin Qubit ◽  
Core Measures

AbstractOperation speed and coherence time are two core measures for the viability of a qubit. Strong spin-orbit interaction (SOI) and relatively weak hyperfine interaction make holes in germanium (Ge) intriguing candidates for spin qubits with rapid, all-electrical coherent control. Here we report ultrafast single-spin manipulation in a hole-based double quantum dot in a germanium hut wire (GHW). Mediated by the strong SOI, a Rabi frequency exceeding 540 MHz is observed at a magnetic field of 100 mT, setting a record for ultrafast spin qubit control in semiconductor systems. We demonstrate that the strong SOI of heavy holes (HHs) in our GHW, characterized by a very short spin-orbit length of 1.5 nm, enables the rapid gate operations we accomplish. Our results demonstrate the potential of ultrafast coherent control of hole spin qubits to meet the requirement of DiVincenzo’s criteria for a scalable quantum information processor.

Engineering Electronic Structure to Protect Phase Memory in Molecular Qubits by Minimising Orbital Angular Momentum

2018 ◽  
Author(s):  
Ana Maria Ariciu ◽  
David H. Woen ◽  
Daniel N. Huh ◽  
Lydia Nodaraki ◽  
Andreas Kostopoulos ◽  
...  
Keyword(s):  
Electron Spin ◽  
Quantum Coherence ◽  
Quantum Information Processing ◽  
Pulse Sequences ◽  
Grover Algorithm ◽  
Ligand Shell ◽  
Information Strategies ◽  
Spin Qubit ◽  
Molecular Spin ◽  
The Impact

Using electron spins within molecules for quantum information processing (QIP) was first proposed by Leuenberger and Loss (1), who showed how the Grover algorithm could be mapped onto a Mn12 cage (2). Since then several groups have examined two-level (S = ½) molecular spin systems as possible qubits (3-12). There has also been a report of the implementation of the Grover algorithm in a four-level molecular qudit (13). A major challenge is to protect the spin qubit from noise that causes loss of phase information; strategies to minimize the impact of noise on qubits can be categorized as corrective, reductive, or protective. Corrective approaches allow noise and correct for its impact on the qubit using advanced microwave pulse sequences (3). Reductive approaches reduce the noise by minimising the number of nearby nuclear spins (7-11), and increasing the rigidity of molecules to minimise the effect of vibrations (which can cause a fluctuating magnetic field via spin-orbit coupling) (9,11); this is essentially engineering the ligand shell surrounding the electron spin. A protective approach would seek to make the qubit less sensitive to noise: an example of the protective approach is the use of clock transitions to render spin states immune to magnetic fields at first order (12). Here we present a further protective method that would complement reductive and corrective approaches to enhancing quantum coherence in molecular qubits. The target is a molecular spin qubit with an effective 2S ground state: we achieve this with a family of divalent rare-earth molecules that have negligible magnetic anisotropy such that the isotropic nature of the electron spin renders the qubit markedly less sensitive to magnetic noise, allowing coherent spin manipulations even at room temperature. If combined with the other strategies, we believe this could lead to molecular qubits with substantial advantages over competing qubit proposals.<br>

scholarly journals Robust and fast post-processing of single-shot spin qubit detection events with a neural network

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tom Struck ◽  
Javed Lindner ◽  
Arne Hollmann ◽  
Floyd Schauer ◽  
Andreas Schmidbauer ◽  
...  
Keyword(s):  
Neural Network ◽  
Neural Networks ◽  
Bayesian Inference ◽  
Rabi Oscillation ◽  
Detection Methods ◽  
Measured Signal ◽  
Single Shot ◽  
Post Processing ◽  
Readout Signal ◽  
Spin Qubit

AbstractEstablishing low-error and fast detection methods for qubit readout is crucial for efficient quantum error correction. Here, we test neural networks to classify a collection of single-shot spin detection events, which are the readout signal of our qubit measurements. This readout signal contains a stochastic peak, for which a Bayesian inference filter including Gaussian noise is theoretically optimal. Hence, we benchmark our neural networks trained by various strategies versus this latter algorithm. Training of the network with 106 experimentally recorded single-shot readout traces does not improve the post-processing performance. A network trained by synthetically generated measurement traces performs similar in terms of the detection error and the post-processing speed compared to the Bayesian inference filter. This neural network turns out to be more robust to fluctuations in the signal offset, length and delay as well as in the signal-to-noise ratio. Notably, we find an increase of 7% in the visibility of the Rabi oscillation when we employ a network trained by synthetic readout traces combined with measured signal noise of our setup. Our contribution thus represents an example of the beneficial role which software and hardware implementation of neural networks may play in scalable spin qubit processor architectures.

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