A quantum simulator is a type of quantum computer that controls the interactions between quantum bits (or qubits) in a way that can be mapped to certain quantum many-body problems. As it becomes ...possible to exert more control over larger numbers of qubits, such simulators will be able to tackle a wider range of problems, such as materials design and molecular modelling, with the ultimate limit being a universal quantum computer that can solve general classes of hard problems. Here we use a quantum simulator composed of up to 53 qubits to study non-equilibrium dynamics in the transverse-field Ising model with long-range interactions. We observe a dynamical phase transition after a sudden change of the Hamiltonian, in a regime in which conventional statistical mechanics does not apply. The qubits are represented by the spins of trapped ions, which can be prepared in various initial pure states. We apply a global long-range Ising interaction with controllable strength and range, and measure each individual qubit with an efficiency of nearly 99 per cent. Such high efficiency means that arbitrary many-body correlations between qubits can be measured in a single shot, enabling the dynamical phase transition to be probed directly and revealing computationally intractable features that rely on the long-range interactions and high connectivity between qubits.
Spiral CT of the pancreas Dupuy, D E; Costello, P; Ecker, C P
Radiology,
06/1992, Letnik:
183, Številka:
3
Journal Article
Recenzirano
Computed tomography (CT) is the modality of choice for evaluation of pancreatic disease. In this prospective study, images obtained with spiral CT, which enables examination of a region of the body ...in a single breath-hold, were compared with those obtained by means of dynamic CT with automatic table incrementation in two groups of 30 patients referred for suspected disease of the pancreas. In both groups, vascular opacification and anatomic detail were analyzed with a grading system (1 = poor, 2 = good, 3 = excellent). Vascular opacification received mean grades of 2.78 and 2.33 in the spiral CT and control groups, respectively. Anatomic detail received mean grades of 2.63 and 2.42 in the spiral CT and control groups, respectively. Respiratory motion artifact was absent in all spiral CT examinations but was present in 17 of 30 control CT examinations. Images obtained with spiral CT showed superior vascular opacification and reduced respiratory artifact with smaller amounts of contrast agent (90 mL vs 120 mL) compared with those obtained with dynamic CT.
We report a search for a heavy neutral lepton (HNL) that mixes predominantly with ν τ . The search utilizes data collected with the Belle detector at the KEKB asymmetric energy e + e − collider. The ...data sample was collected at and just below the center-of-mass energies of the ϒ ( 4 S ) and ϒ ( 5 S ) resonances and has an integrated luminosity of 915 fb − 1 , corresponding to ( 836 ± 12 ) × 10 6 e + e − → τ + τ − events. We search for production of the HNL (denoted N ) in the decay τ − → π − N followed by its decay via N → μ + μ − ν τ . The search focuses on the parameter-space region in which the HNL is long-lived, so that the μ + μ − originate from a common vertex that is significantly displaced from the collision point of the KEKB beams. Consistent with the expected background yield, one event is observed in the data sample after application of all the event-selection criteria. We report limits on the mixing parameter of the HNL with the τ neutrino as a function of the HNL mass. Published by the American Physical Society 2024
A
bstract
We report the first measurement of the inclusive
e
+
e
−
→
$$ b\overline{b} $$
b
b
¯
→
$$ {D}_s^{\pm } $$
D
s
±
X
and
e
+
e
−
→
$$ b\overline{b} $$
b
b
¯
→ D
0
/
$$ {\overline{D}}^0 $$
D
¯
...0
X
cross sections in the energy range from 10
.
63 to 11
.
02 GeV. Based on these results, we determine
σ
(
e
+
e
−
→
$$ {B}_s^0{\overline{B}}_s^0 $$
B
s
0
B
¯
s
0
X
) and
σ
(
e
+
e
−
→
$$ B\overline{B} $$
B
B
¯
X
) in the same energy range. We measure the fraction of
$$ {B}_s^0 $$
B
s
0
events at Υ(10860) to be
f
s
= (
$$ {22.0}_{-2.1}^{+2.0} $$
22.0
−
2.1
+
2.0
)%. We determine also the ratio of the
$$ {B}_s^0 $$
B
s
0
inclusive branching fractions
$$ \mathcal{B} $$
B
(
$$ {B}_s^0 $$
B
s
0
→ D
0
/
$$ {\overline{D}}^0 $$
D
¯
0
X
)
/
$$ \mathcal{B} $$
B
(
$$ {B}_s^0 $$
B
s
0
→
$$ {D}_s^{\pm } $$
D
s
±
X
) = 0
.
416 ± 0
.
018 ± 0
.
092. The results are obtained using the data collected with the Belle detector at the KEKB asymmetric-energy
e
+
e
−
collider.
The effectiveness of spiral computed tomography (CT) of the thorax performed with 60 mL of 60% contrast material was compared with that of conventional dynamic incremental CT performed with 120 mL of ...60% contrast material. Fifty patients in whom contrast material-enhanced thoracic CT examination was necessary were assigned to undergo either spiral CT or dynamic incremental CT. Vascular opacification and mediastinal-lung image quality were graded independently by two observers. Vascular opacification and lung image quality were better with spiral CT than with conventional CT. Results of this pilot study encourage the use of spiral CT to decrease the volume of contrast medium used in patients undergoing thoracic CT.
The blood flow rate is the only parameter that can be controlled during the operation of an intracorporeal membrane oxygenator that significantly influences the gas exchange rate. Due to anatomical ...size restrictions, the catheter is of limited size and the tight packaging does not allow for placement of a dedicated flow rate sensor. Therefore, for a flow rate control system, the correct estimation of the blood flow rate is essential. In this work, a system specific flow rate estimation method is presented based on motor current and motor speed measurements. A training data set of motor current - I and rotational speed - ω, as well as volumetric flow rate - Q were recorded in an in-vitro model of the intracorporeal membrane oxygenator. A 40/60 water/glycerol mixture was used to approximate the dynamic properties of blood. The rotational speed of the motor was varied in a range of 10000 to 30000 RPM. For each motor speed, the hydraulic resistance of the system was varied with a throttle resulting in different flow rate values. Additionally, a test data set was acquired consisting of different rotational speed, hydraulic resistance, and flow rate triplets. The I, ω and Q training data was used to construct a fitting surface of the type Q(I, ω) by a regularized cubic spline least-squares approximation method. The surface was defined in a grid of 591x591 points with Imin=-70 mA, Imax=520 mA, ωmin=500 RPM, ωmax=30000 RPM. The test set of I – ω pairs was then used to predict Q by means of a nearest neighbor search in the modeled surface. A correlation coefficient of r=0.96 was achieved between the estimated and measured flow rates of the water/glycerol mixture. The strong correlation between estimated and measured flow rate suggests that sensorless flow rate control is possible.
A bstract We report the first measurement of the inclusive e + e − → $$ b\overline{b} $$ b b ¯ → $$ {D}_s^{\pm } $$ D s ± X and e + e − → $$ b\overline{b} $$ b b ¯ → D 0 / $$ {\overline{D}}^0 $$ D ¯ ...0 X cross sections in the energy range from 10 . 63 to 11 . 02 GeV. Based on these results, we determine σ ( e + e − → $$ {B}_s^0{\overline{B}}_s^0 $$ B s 0 B ¯ s 0 X ) and σ ( e + e − → $$ B\overline{B} $$ B B ¯ X ) in the same energy range. We measure the fraction of $$ {B}_s^0 $$ B s 0 events at Υ(10860) to be f s = ( $$ {22.0}_{-2.1}^{+2.0} $$ 22.0 − 2.1 + 2.0 )%. We determine also the ratio of the $$ {B}_s^0 $$ B s 0 inclusive branching fractions $$ \mathcal{B} $$ B ( $$ {B}_s^0 $$ B s 0 → D 0 / $$ {\overline{D}}^0 $$ D ¯ 0 X ) / $$ \mathcal{B} $$ B ( $$ {B}_s^0 $$ B s 0 → $$ {D}_s^{\pm } $$ D s ± X ) = 0 . 416 ± 0 . 018 ± 0 . 092. The results are obtained using the data collected with the Belle detector at the KEKB asymmetric-energy e + e − collider.
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