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| 2. |
- Huang, Guanhao, et al.
(författare)
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Measuring the quantum vibrations of a small drum at room temperature
- 2024
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- A combination of technical improvements in noise mitigation enabled the observation of the quantum force of light on a millimetre-scale drum at room temperature. This experimental system permits the drum's position to be measured with an accuracy close to the quantum limit.
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| 3. |
- Azimi Mousolou, Vahid, et al.
(författare)
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Universal Non-adiabatic Holonomic Gates in Quantum Dots and Single-Molecule Magnets
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Geometric manipulation of a quantum system offers a method for fast, universal, and robust quantum information processing. Here, we propose a scheme for universal all-geometric quantum computation using non-adiabatic quantum holonomies. We propose three different realizations of the scheme based on an unconventional use of quantum dot and single-molecule magnet devices,which offer promising scalability and robust efficiency.
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| 4. |
- Berkowicz, Sharon, 1994-, et al.
(författare)
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Resolving nanoscale dynamics during a liquid-liquid transition in supercooled glycerol-water solutions
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- It is proposed that a liquid-liquid transition (LLT), related to the hypothesized transition between high- and low-density liquids (HDL, LDL) in pure water, also exists in supercooled aqueous mixtures. However, experimental observations of the LLT in the supercooled solution is often complicated by the overlap with freezing. Here, we conducted an experiment probing the hypothesized LLT in deeply supercooled 16.5 mol% glycerol-water solution, combining X-ray photon correlation spectroscopy (XPCS), ultra small-angle X-ray scattering (USAXS) and wide-angle X-ray scattering (WAXS). This approach allows us to capture simultaneous, discontinuous structural and dynamic changes within the supercooled liquid following quenching to cryogenic temperatures (172-182 K). We observe changes in the inter-atomic liquid structure (from WAXS) as well as in the nanoscale structure and dynamics (from USAXS/XPCS), resembling a first-order LLT between HDL-like to LDL-like liquid. Importantly, we find that the LLT precedes the onset of ice crystalliization, which we can distinguish based on the advent of ice bragg peaks in WAXS. In addition, analysis of the two-time correlation (TTC) function from XPCS enables us to follow the dynamics during the LLT, which indicates super-diffusive ballistic-like motion and a gradual slowdown towards an arrested state upon freezing, consistent with an LLT via spinodal decomposition. We conclude that these results indicate the existence of a first-order LLT in supercooled glycerol-water solutions at intermediate glycerol concentrations, similar to that hypothesized for pure water at elevated pressures.
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| 5. |
- Berkowicz, Sharon, 1994-, et al.
(författare)
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Unveiling the Structure and Thermodynamics of Deeply Supercooled Glycerol-Water Microdroplets with Ultrafast X-ray Scattering
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The liquid-liquid critical point (LLCP) hypothesis of water suggests that water exists in two structurally distinct liquid states, high- and low-density liquid (HDL, LDL), with an LLCP hidden in the supercooled regime at elevated pressures. However, its consequences for solvation and structural dynamics in aqueous solutions remain to be explored. Here, we probe the structure and thermodynamics of deeply supercooled microdroplets of prototypical aqueous solutions of glycerol. The combination of rapid evaporative cooling with ultrafast small- and wide-angle X-ray scatter-ing (SAXS, WAXS) allows us to outrun crystallization and gain access to the largely unexplored deeply supercooled dilute regime (3.2 mol% glycerol) down to T ≈ 229 K, which is not accessible by conventional cooling methods. The experimental results, and complementary molecular dynamics(MD) simulations, indicate an increase in the tetrahedral coordination and enhancement of HDL-and LDL-like density fluctuations upon supercooling. In addition, the extended temperature range of the MD simulations reveals a maximum in the isothermal compressibility at T ≈ 220 K, indicating the location of a Widom line shifted to slightly lower temperatures compared to that of pure water. We conclude that the apparent effect of the presence of glycerol molecules on the water hydrogen-bond structure resembles that of pressure. This opens the possibility to search for the existence of an LLCP in these aqueous solutions simply by varying the solute concentration.
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| 6. |
- Björnson, Kristofer, et al.
(författare)
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Solid state Stern-Gerlach spin-splitter for magnetic field sensoring, spintronics, and quantum computing
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We show that the edge of a two-dimensional topological insulator can be used to construct a solid state Stern-Gerlach spin-splitter. By threading such a Stern-Gerlach apparatus with a magnetic flux, Ahranov-Bohm like interference effects are introduced. Using ferromagnetic leads, the setup can be used to both measure magnetic flux and as a spintronics switch. With normal metallic leads a switchable spintronics NOT-gate can be implemented. Furthermore, we show that a sequence of such devices can be used to construct a single-qubit SU(2)-gate, one of the two gates required for a universal quantum computer. The field sensitivity, or switching field, b is related to the device characteristic size r through b=ℏ/qr2, with q the unit of electric charge.
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| 9. |
- Shulumba, Nina, et al.
(författare)
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Influence of vibrational free energy on the phase stability of alloys from first principles
- 2015
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We have developed a method to accurately and efficiently determine the vibrational free energy as a function of temperature and pressure for substitutional alloys from first principles. Taking the example of the technologically important hard coating alloy Ti1-xAlxN as an example, we investigate the effect on the vibrational free energy of substituting Ti for other group IV elements. By constructing the phase diagrams for these three alloys, we show why Zr1-xAlxN and Hf1-xAlxN are so difficult to experimentally synthesise in a metastable solid solution: both have solubility regions that span only a small low-AlN concentration range at temperatures above 1500 K. Moreover, Hf1-xAlxN is dynamically unstable at low temperatures and across most of the concentration range. We also show the chemical and thermal expansion effects dominate mass disorder in the Gibbs free energy of mixing.
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