115 research outputs found
Attribute Assignment to Point Cloud Data and Its Usage
In recent years, with the development of laser measurement technology, utilization of point cloud data is progressing. However, since point cloud data does not contain attribute information, the usability of the data is low. It is possible to consider that by assigning attributes to the nonattribute point cloud data, this can lead to the usage of point cloud data in each phase of life cycle of construction: design, construction, and maintenance. Therefore, in this paper, the authors have proposed an attribute assignment method for point cloud data. In addition, the authors proposed the way to use attributed point cloud data, the usage as objects, data linkage, and visualization by using the attribute assignment method. Point cloud data of a dam was used as a case study for the proposed method and the usage
Feedback-based active reset of a spin qubit in silicon
Feedback control of qubits is a highly demanded technique for advanced
quantum information protocols such as quantum error correction. Here we
demonstrate active reset of a silicon spin qubit using feedback control. The
active reset is based on quantum non-demolition readout of the qubit and
feedback according to the readout results, which is enabled by hardware data
processing and sequencing. We incorporate a cumulative readout technique to the
active reset protocol, enhancing initialization fidelity above a limitation
imposed by accuracy of the single QND measurement fidelity. Based on an
analysis of the reset protocol, we suggest a way to achieve the initialization
fidelity sufficient for the fault-tolerant quantum computation
A shuttling-based two-qubit logic gate for linking distant silicon quantum processors
Control of entanglement between qubits at distant quantum processors using a
two-qubit gate is an essential function of a scalable, modular implementation
of quantum computation. Among the many qubit platforms, spin qubits in silicon
quantum dots are promising for large-scale integration along with their
nanofabrication capability. However, linking distant silicon quantum processors
is challenging as two-qubit gates in spin qubits typically utilize short-range
exchange coupling, which is only effective between nearest-neighbor quantum
dots. Here we demonstrate a two-qubit gate between spin qubits via coherent
spin shuttling, a key technology for linking distant silicon quantum
processors. Coherent shuttling of a spin qubit enables efficient switching of
the exchange coupling with an on/off ratio exceeding 1,000 , while preserving
the spin coherence by 99.6% for the single shuttling between neighboring dots.
With this shuttling-mode exchange control, we demonstrate a two-qubit
controlled-phase gate with a fidelity of 93%, assessed via randomized
benchmarking. Combination of our technique and a phase coherent shuttling of a
qubit across a large quantum dot array will provide feasible path toward a
quantum link between distant silicon quantum processors, a key requirement for
large-scale quantum computation
Rapid single-shot parity spin readout in a silicon double quantum dot with fidelity exceeding 99 %
Silicon-based spin qubits offer a potential pathway toward realizing a
scalable quantum computer owing to their compatibility with semiconductor
manufacturing technologies. Recent experiments in this system have demonstrated
crucial technologies, including high-fidelity quantum gates and multiqubit
operation. However, the realization of a fault-tolerant quantum computer
requires a high-fidelity spin measurement faster than decoherence. To address
this challenge, we characterize and optimize the initialization and measurement
procedures using the parity-mode Pauli spin blockade technique. Here, we
demonstrate a rapid (with a duration of a few us) and accurate (with >99%
fidelity) parity spin measurement in a silicon double quantum dot. These
results represent a significant step forward toward implementing
measurement-based quantum error correction in silicon
Spatial noise correlations beyond nearest-neighbor in Si/SiGe spin qubits
We detect correlations in qubit-energy fluctuations of non-neighboring qubits
defined in isotopically purified Si/SiGe quantum dots. At low frequencies
(where the noise is strongest), the correlation coefficient reaches 10% for a
next-nearest-neighbor qubit-pair separated by 200 nm. Assigning the observed
noise to be of electrical origin, a simple theoretical model quantitatively
reproduces the measurements and predicts a polynomial decay of correlations
with interqubit distance. Our results quantify long-range correlations of noise
dephasing quantum-dot spin qubits arranged in arrays, essential for scalability
and fault-tolerance of such systems.Comment: 11 pages, 8 figure
Hamiltonian Phase Error in Resonantly Driven CNOT Gate Above the Fault-Tolerant Threshold
Because of their long coherence time and compatibility with industrial
foundry processes, electron spin qubits are a promising platform for scalable
quantum processors. A full-fledged quantum computer will need quantum error
correction, which requires high-fidelity quantum gates. Analyzing and
mitigating the gate errors are useful to improve the gate fidelity. Here, we
demonstrate a simple yet reliable calibration procedure for a high-fidelity
controlled-rotation gate in an exchange-always-on Silicon quantum processor
allowing operation above the fault-tolerance threshold of quantum error
correction. We find that the fidelity of our uncalibrated controlled-rotation
gate is limited by coherent errors in the form of controlled-phases and present
a method to measure and correct these phase errors. We then verify the
improvement in our gate fidelities by randomized benchmark and gate-set
tomography protocols. Finally, we use our phase correction protocol to
implement a virtual, high-fidelity controlled-phase gate.Comment: Main article: 22 pages, 4 figures; Supplementary material: 6 pages, 5
figures, 1 tabl
Clinical approach to renal study incidental to 99mTc-MDP bone scintigraphy
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