Realizing quantum gates with optically-addressable 171^{171}Yb+^{+} ion qudits

The use of multilevel information carriers, also known as qudits, is a promising path for exploring scalability of quantum computing devices. In this work, we present a proof-of-principle realization of a quantum processor that uses optically-addressed $^{171}$Yb$^{+}$ ion qudits in a linear trap. The rich level structure of $^{171}$Yb$^{+}$ ions makes it possible to use the Zeeman sublevels of the quadrupole clock transition at 435.5 nm for efficient and robust qudit encoding. We demonstrate the realization of the universal set of gates consisting of single-qudit rotations and two-qudit entangling operation with a two-ququart system, which is formally equivalent to a universal gate-based four-qubit processor. Our results paves a way towards further studies of more efficient implementations of quantum algorithms with trapped-ion-based processors.Comment: 9 pages, 3 figure

Demonstration of a parity-time symmetry breaking phase transition using superconducting and trapped-ion qutrits

Scalable quantum computers hold the promise to solve hard computational problems, such as prime factorization, combinatorial optimization, simulation of many-body physics, and quantum chemistry. While being key to understanding many real-world phenomena, simulation of non-conservative quantum dynamics presents a challenge for unitary quantum computation. In this work, we focus on simulating non-unitary parity-time symmetric systems, which exhibit a distinctive symmetry-breaking phase transition as well as other unique features that have no counterpart in closed systems. We show that a qutrit, a three-level quantum system, is capable of realizing this non-equilibrium phase transition. By using two physical platforms - an array of trapped ions and a superconducting transmon - and by controlling their three energy levels in a digital manner, we experimentally simulate the parity-time symmetry-breaking phase transition. Our results indicate the potential advantage of multi-level (qudit) processors in simulating physical effects, where additional accessible levels can play the role of a controlled environment.Comment: 14 pages, 9 figure

The ATLAS Transition Radiation Tracker (TRT) proportional drift tube: design and performance

A straw proportional counter is the basic element of the ATLAS Transition Radiation Tracker (TRT). Its detailed properties as well as the main properties of a few TRT operating gas mixtures are described. Particular attention is paid to straw tube performance in high radiation conditions and to its operational stability

The ATLAS TRT electronics

The ATLAS inner detector consists of three sub-systems: the pixel detector spanning the radius range 4cm-20cm, the semiconductor tracker at radii from 30 to 52 cm, and the transition radiation tracker (TRT), tracking from 56 to 107 cm. The TRT provides a combination of continuous tracking with many projective measurements based on individual drift tubes (or straws) and of electron identification based on transition radiation from fibres or foils interleaved between the straws themselves. This paper describes the on and off detector electronics for the TRT as well as the TRT portion of the data acquisition (DAQ) system

Creutzfeldt–Jakob disease in the Republic of Sakha (Yakutia)

Creutzfeldt–Jakob disease (CJD) is a rare neurodegenerative disease caused by the accumulation of the pathological isoform of prion protein. The classic clinical presentation of CJD is characterized by rapidly progressive dementia, ataxia, myoclonus, and akinetic mutism at the terminal stage of the disease. Of the instrumental techniques, brain magnetic resonance imaging plays a leading role in clinical practice. The authors followed up 4 patients with probable CJD in the Republic of Sakha (Yakutia) in 2014 to 2019. All the patients had approximately the same age (50–60 years) at disease onset and onset with non-specific cerebral symptoms. However, the subsequent development of rapidly progressive dementia and other characteristic features might suggest CJD. The patients were found to have characteristic neuroimaging signs as hyperintensity of the caudate nuclei and pulvinars in the fluid-attenuated inversion recovery (FLAIR) and diffusion weighted imaging (DWI) modes to form the typical signal of hockey sticks, as well as hyperintensity of the gray matter in the DWI mode (the symptom of the «Venus necklace»). In 3 patients, the disease ended fatally within a year of its onset. The fourth patient with a disease duration of 6 months is being supervised at home. The authors reason that the diagnosis of CJD is now insufficient due to the similarity of its clinical symptoms at the onset with other disorders, including cerebrovascular and neurodegenerative diseases

Continuous dynamical decoupling of optical 171^{171}Yb+^{+} qudits with radiofrequency fields

The use of multilevel quantum information carriers, also known as qudits, attracts a significant deal of interest as a way for further scalability of quantum computing devices. However, a nontrivial task is to experimentally achieve a gain in the efficiency of realizing quantum algorithms with qudits since higher qudit levels typically have relatively short coherence times compared to qubit states. Here we propose and experimentally demonstrate two approaches for the realization of continuous dynamical decoupling of magnetic-sensitive states with $m_F=\pm1$ for qudits encoded in optical transition of trapped $^{171}$Yb$^{+}$ ions. We achieve improvement in qudit levels coherence time by the order of magnitude (more than 9 ms) without any magnetic shielding, which reveals the potential advantage of the symmetry of the $^{171}$Yb$^{+}$ ion energy structure for counteracting the magnetic field noise. Our results are a step towards the realization of qudit-based algorithms using trapped ions.Comment: 12 pages, 5 figure