25 research outputs found
Muscle-Tendon Complex-Inspired Deformable Exteriors as a Wire-Drive Extension
The 11th International Symposium on Adaptive Motion of Animals and Machines. Kobe University, Japan. 2023-06-06/09. Adaptive Motion of Animals and Machines Organizing Committee.Poster Session P5
Robust Single-Shot Spin Measurement with 99.5% Fidelity in a Quantum Dot Array
We demonstrate a new method for projective single-shot measurement of two
electron spin states (singlet versus triplet) in an array of gate-defined
lateral quantum dots in GaAs. The measurement has very high fidelity and is
robust with respect to electric and magnetic fluctuations in the environment.
It exploits a long-lived metastable charge state, which increases both the
contrast and the duration of the charge signal distinguishing the two
measurement outcomes. This method allows us to evaluate the charge measurement
error and the spin-to-charge conversion error separately. We specify conditions
under which this method can be used, and project its general applicability to
scalable quantum dot arrays in GaAs or silicon.Comment: 13 pages, 3 figure
Quantum nondemolition measurement of an electron spin qubit
Measurement of quantum systems inevitably involves disturbance in various
forms. Within the limits imposed by quantum mechanics, however, one can design
an "ideal" projective measurement that does not introduce a back action on the
measured observable, known as a quantum nondemolition (QND) measurement. Here
we demonstrate an all-electrical QND measurement of a single electron spin in a
gate-defined quantum dot via an exchange-coupled ancilla qubit. The ancilla
qubit, encoded in the singlet-triplet two-electron subspace, is entangled with
the single spin and subsequently read out in a single shot projective
measurement at a rate two orders of magnitude faster than the spin relaxation.
The QND nature of the measurement protocol is evidenced by observing a
monotonic increase of the readout fidelity over one hundred repetitive
measurements against arbitrary input states. We extract information from the
measurement record using the method of optimal inference, which is tolerant to
the presence of the relaxation and dephasing. The QND measurement allows us to
observe spontaneous spin flips (quantum jumps) in an isolated system with small
disturbance. Combined with the high-fidelity control of spin qubits, these
results pave the way for various measurement-based quantum state manipulations
including quantum error correction protocols.Comment: This is a pre-print of an article published in Nature Nanotechnology.
The final authenticated version is available online at:
https://doi.org/10.1038/s41565-019-0426-
Subtotal esophagectomy and concurrent reconstruction with free jejunal flap for primary esophageal cancer after pancreatoduodenectomy
Background Pancreatoduodenectomy and subtotal esophagectomy are widely considered the most invasive and difficult surgical procedures in gastrointestinal surgery. Subtotal esophagectomy after pancreatoduodenectomy is expected to be extremely difficult due to complicated anatomical changes, and selecting an appropriate intestinal reconstruction method will also be a difficult task. Therefore, perhaps because the method is considered impossible, there have been few reports of subtotal esophagectomy after pancreatoduodenectomy.
Case presentation A 73-year-old man with a history of pancreatoduodenectomy was diagnosed with superficial thoracic esophageal squamous cell carcinoma. Definitive chemoradiation therapy was recommended at another hospital; however, he visited our department to undergo surgery. We performed the robot-assisted thoracoscopic subtotal esophagectomy. There were some difficulties with the reconstruction: the gastric tube could not be used, the reconstruction was long, and the organs reconstructed in the previous surgery had to be preserved. However, the concurrent reconstruction was achieved with the help of a free jejunal flap and vascular reconstruction. All reconstructions from the previous surgery, including the remnant stomach, were preserved via regional abdominal lymph node dissection. After reconstruction, intravenous indocyanine green showed that circulation in the reconstructed intestines was preserved. On postoperative day 1, no recurrent nerve paralysis was observed during laryngoscopy. The patient could start oral intake smoothly 2 weeks after surgery and did not exhibit any postoperative complications related to the reconstruction. The patient was transferred to another hospital on postoperative day 21.
Conclusions Owing to the free jejunal flap interposition method, we safely performed one stage subtotal esophagectomy and concurrent reconstruction, preservation of the remnant stomach, and pancreaticobiliary reconstruction in patients with a history of pancreatoduodenectomy. We believe that this method is acceptable and useful for patients undergoing complicated reconstruction
Safe and curative modified two-stage operation for T4 esophageal cancer after definitive chemoradiotherapy: a case report
Background The prognosis of esophageal cancer (EC) with organ invasion is extremely poor. In these cases, definitive chemoradiotherapy (CRT) followed by salvage surgery can be planned; however, the issue of high morbidity and mortality rates persists. Herein, we report the long-term survival of a patient with EC and T4 invasion who underwent a modified two-stage operation after definitive CRT.
Case presentation A 60-year-old male presented with type 2 upper thoracic EC with tracheal invasion. First, definitive CRT was performed, which resulted in tumor shrinkage and improvement in the tracheal invasion. However, an esophagotracheal fistula subsequently developed, and the patient was treated with fasting and antibiotics. Although the fistula recovered, severe esophageal stenoses made oral intake impossible. To improve quality of life and cure the EC, a modified two-stage operation was planned. In the first surgery, an esophageal bypass was performed using a gastric tube with cervical and abdominal lymph node dissections. After confirming improved nutritional status and absence of distant metastasis, the second surgery was performed with subtotal esophagectomy, mediastinal lymph node dissection, and tracheobronchial coverage of the fistula. The patient discharged without major complications after radical resection and has been recurrence-free for 5 years since the start of treatment.
Conclusion A standard curative strategy could be difficult for EC with T4 invasion due to differences in the invaded organs, presence of complications, and patient condition. Therefore, patient-tailored treatment plans are needed, including a modified two-stage operation
Dedifferentiated Liposarcoma in the Spermatic Cord Finally Diagnosed at 7th Resection of Recurrence: A Case Report and Bibliographic Consideration
Coherence of a driven electron spin qubit actively decoupled from quasi-static noise
The coherence of electron spin qubits in semiconductor quantum dots suffers
mostly from low-frequency noise. During the last decade, efforts have been
devoted to mitigate such noise by material engineering, leading to substantial
enhancement of the spin dephasing time for an idling qubit. However, the role
of the environmental noise during spin manipulation, which determines the
control fidelity, is less understood. We demonstrate an electron spin qubit
whose coherence in the driven evolution is limited by high-frequency charge
noise rather than the quasi-static noise inherent to any semiconductor device.
We employed a feedback control technique to actively suppress the latter,
demonstrating a -flip gate fidelity as high as in a
gallium arsenide quantum dot. We show that the driven-evolution coherence is
limited by the longitudinal noise at the Rabi frequency, whose spectrum
resembles the noise observed in isotopically purified silicon qubits.Comment: 10 pages, 7 figure