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A versatile magnetometer must deliver a readable response when exposed to target fields in a wide range of parameters. In this work, we experimentally demonstrate that the combination of $^{171}$Yb$^{+}$ atomic sensors with adequately trained neural networks enables to investigate target fields in distinct challenging scenarios. In particular, we characterize radio frequency (RF) fields in the presence of large shot noise, including the limit case of continuous data acquisition via single-shot measurements. Furthermore, by incorporating neural networks we significantly extend the working regime of atomic magnetometers into scenarios in which the RF driving induces responses beyond their standard harmonic behavior. Our results indicate the benefits to integrate neural networks at the data processing stage of general quantum sensing tasks to decipher the information contained in the sensor responses., Comment: 11 pages, 8 figures

The Dysphagia Handicap Index (DHI) is a valid Health-related Quality of Life (HRQoL) 25-item questionnaire assessing the physical, functional, and emotional aspects of patients with oropharyngeal dysphagia (OD), of heterogeneous etiologies. The purpose of this study is to translate and validate the European Portuguese-DHI (EP-DHI). This is a prospective study that was carried out at Centro Hospitalar Universitário do Porto (CHUPorto). The generated EP-DHI was administered to 132 patients with OD and 112 healthy control subjects. 132 patients undergoing fiberoptic endoscopic examination of swallowing (FEES). 15 patients were contacted by phone, 2 or 3 weeks later after the first interview to repeat the questionnaire. The validity of concurrent criteria was evaluated by comparing the results of the EP-DHI score with the score attributed to the pathological findings found in FEES and, consequently, Functional Oral Intake Scale (FOIS). The internal consistency of EP-DHI was successful: Cronbach's alpha coefficient for total EP-DHI was 0.874. The test-retest reliability for the total and the three EP-DHI subscales obtained a Pearson's correlation coefficient ranged from 0.990 to 0.712. This study demonstrates that EP-DHI is a valid tool for self-assessment of the handicapping effect of dysphagia on physical, functional, and emotional aspects of patient's quality of life, among an European Portuguese sample.

We present a protocol that detects molecular conformational changes with two nitroxide electron-spin labels and a nitrogen-vacancy (NV) center in diamond. More specifically, we demonstrate that the NV can detect en- ergy shifts induced by the coupling between electron-spin labels. The protocol relies on the judicious application of microwave and radiofrequency pulses in a range of parameters that ensures stable nitroxide resonances. Fur- thermore, we demonstrate that our scheme is optimized by using nitroxides with distinct nitrogen isotopes. We develop a simple theoretical model that we combine with Bayesian inference techniques to demonstrate that our method enables the detection of conformational changes in ambient conditions including strong NV dephasing rates as a consequence of the diamond surface proximity and nitroxide thermalization mechanisms. Finally, we counter-intuitively show that with our method the small residual effect of random molecular tumbling becomes a resource that can be exploited to extract inter-label distances.

Introduction and objectives Congenital atresia of the external auditory canal (EAC) is a congenital defect present in one in every 10,000–20,000 births. It causes conductive hearing loss, with an air-bone gap of 50–60 dB. Early amplification is essential in bilateral cases to ensure normal language development. The aim of this study is to present the osseointegrated hearing implant as a treatment for bilateral EAC atresia, reviewing the audiometric results and the rate of complications. Material and methods Retrospective analysis of patients diagnosed with bilateral congenital EAC atresia under follow-up in the pediatric ENT clinic of the ENT and Head and Neck Surgery department of a Portuguese Tertiary Hospital, between 2003 and 2019. We reviewed the medical records and collected information on the assessment of the initial audiometric status. In the cases submitted for implantation with an osseointegrated hearing implant, we analyzed the details of follow-up, including immediate and long-term post-operative complications, as well as the audiometric results. Results We present 8 pediatric patients, 6 girls and 2 boys, with a diagnosis of bilateral congenital EAC atresia. The audiometric assessment revealed moderate to severe bilateral conductive hearing loss with a mean speech recognition threshold (SRT) of 51 dB. Six patients underwent osseointegrated hearing implantation. All 6 patients showed good audiometric results, with an average SRT of 20 dB and closure of the air-bone gap. Conclusions The osseointegrated hearing implant was an effective treatment option in these patients, without significant morbidity or complications. Osseointegrated hearing implantation should be considered first line treatment for children with bilateral congenital EAC atresia, as it presents good functional results and a high level of patient satisfaction.

BACKGROUND Vena cava anomalies are rare congenital defects due to incorrect development during fetal life, ranging from minor asymptomatic anatomic variations to complex life-threatening abnormalities. Echocardiography plays a fundamental role in the diagnosis, with advanced imaging techniques allowing detailed anatomic delineation. Invasive cardiology techniques are a promising therapeutic approach, but surgery is probably the best option when diffuse compromise of the systemic veins is present. CASE REPORT An 8-month-old infant presenting episodes of labial cyanosis and a failure to thrive was diagnosed with severe superior vena cava (SVC) stenosis at the right atrium ostium, with decompression via azygos vein and mild inferior vena cava (IVC) stenosis. The patient was referred for surgery, with IVC enlargement and removal of a fibromuscular tissue band on the anterior aspect of the SVC ostium. At a 6-month follow-up, the patient is asymptomatic, with excellent surgical outcome. To the authors' knowledge, only two cases of congenital SVC stenosis have been previously described.

Abnormal distribution may put coronary arteries at risk of damage during valvular surgery, especially if it is not identified during a preoperative examination. In this case report, we describe an approach to an anomalous right coronary artery during aortic valve replacement.

En este artículo presentamos un ejercicio de evaluación causal en el contexto del perfilado estadístico aplicado a un programa de empleo creado por la Fundación “La Caixa” y denominado Incorpora. Este programa consiste en un mecanismo de apoyo y recolocación en el mercado de trabajo de personas en riesgo de exclusión. Nuestros resultados apuntan a que la formación impartida dentro del programa contribuye a una mejora general de la empleabilidad media de los participantes en el programa, pero se observa cómo este efecto decae en el tiempo que el beneficiario está desempleado. Por otra parte, encontramos que el programa Incorpora mejora la probabilidad de encontrar y retener el empleo, así como el tiempo trabajado e incluso el salario una vez reempleado, para todos los colectivos analizados sin importar el género, nacionalidad, sector previo de empleo o experiencia laboral previa. Concretamente, la empleabilidad aumenta entre 3 y 4 puntos porcentuales gracias al programa y el efecto sobre el número de meses acumulados en el empleo se sitúa, dependiendo de la cohorte, entre 3 y 4 meses tres años después de salir del mismo.

Background Chylothorax in neonates results from leakage of lymph from thoracic lymphatic ducts and is mainly congenital or posttraumatic. The clinical course of the effusion is heterogeneous, and consensus on treatment, timing, and modalities of measures has not yet been established. This review aims to present, along with levels of evidence and recommendation grades, all current therapeutic possibilities for the treatment of chylothorax in neonates. Methods An extensive search of publications between 1970 and 2020 was performed in the PubMed, Cochrane Database of Systematic Reviews, and UpToDate databases. A stepwise approach algorithm was proposed for both congenital and traumatic conditions to guide the clinician in a rational and systematic way for approaching the treatment of neonates with chylothorax. Discussion and conclusion The treatment strategy for neonatal chylothorax generally involves supportive care and includes drainage and procedures to reduce chyle flow. A stepwise approach starting with the least invasive method is advocated. Progression in the invasiveness of treatment options is determined by the response to previous treatments. A practical stepwise approach algorithm is proposed for both, congenital and traumatic chylothoraces.

Our objective was to examine the results of ECMO post cardiotomy in Centro Hospitalar Universitário S. João (CHUSJ).Between 2011 and 2019, 13 patients were cannulated for refractory cardiogenic shock post-cardiotomy; 8 (61,5%) male and 5 (38,5%) female. Patients under 18 years old were excluded. Data was collected from hospital archives concerning preoperative comorbidities, open-heart surgery procedure, dates of ECMO cannulation and decannulation, postoperative complications, hospital mortality and cause of death. Follow-up was obtained by review of the last outpatient observation. The outcomes investigated were hospital mortality and survival at 12, 36 and 60 months.After a median ECMO-VA therapy of 6 days (1-16 days), 7 (53,8%) patients were successfully decannulated; from these 2 succumbed from stroke and septic shock, one is still in intermediate care convalescing steadily and 4 were discharged. Overall 8 (61,5%) patients died. 5 (38,5%) survived, 4 were discharged home and 1 is still in intermediate care. Survival (after discharge) at 12, 36 and 60 months was respectively 25%, 16,7% and 8,3%. Regarding postoperative complications, reoperation for bleeding was necessary in 5 (38.5%), stroke was diagnosed in 2 (15,4%), dialysis in 6 (46,2%), leg ischemia affected 5 (38,5%) and mediastinitis occurred in 1 (7,7%).VA ECMO saves a life in each three patients suffering from refractory cardiogenic shock after cardiac surgery. Despite risks associated with advanced cardiopulmonary support, survivors maintain good health condition.

During valvular surgery, abnormal coronary distribution, especially if unidentified by preoperative exams, may put coronary arteries at risk of damage. In this case report, we describe the approach to an anomalous right coronary artery during aortic valve replacement.

7 pags., 3 figs., 1 app., Quantum sensors typically translate external fields into a periodic response whose frequency is then determined by analyses performed in Fourier space. This allows for a linear inference of the parameters that characterize external signals. In practice, however, quantum sensors are able to detect fields only in a narrow range of amplitudes and frequencies. A departure from this range, as well as the presence of significant noise sources and short detection times, lead to a loss of the linear relationship between the response of the sensor and the target field, thus limiting the working regime of the sensor. Here we address these challenges by means of a Bayesian inference approach that is tolerant to strong deviations from desired periodic responses of the sensor and is able to provide reliable estimates even with a very limited number of measurements. We demonstrate our method for an 171Yb+ trapped-ion quantum sensor but stress the general applicability of this approach to different systems., We acknowledge financial support from the Spanish Government via PGC2018-095113-B-I00 (MCIU/AEI/FEDER, UE) and EUR2020-112117, the Basque Government via IT986-16, as well as from QMiCS (820505) and OpenSuperQ (820363) of the EU Flagship on Quantum Technologies, and the EU FET Open Grant Quromorphic. J.C. acknowledges the Ramón y Cajal program (RYC2018- 025197-I) and support from the UPV/EHU through the grant EHUrOPE. M.B.P. acknowledges support from the ERC Synergy Grant HyperQ, the EU Flagship project AsteriQs, and the BMBF projects Nanospin and DiaPol. J.F.H. acknowledges support from the Alexander von Humboldt Foundation in the form of a FeodorLynen Fellowship. R.P. and M.P. acknowledge support from the SFI-DfE Investigator Programme (Grant No. 15/IA/2864). M.P. acknowledges the H2020 Collaborative Project TEQ (Grant Agreement No. 766900), the Leverhulme Trust Research Project Grant UltraQuTe (Grant No. RGP-2018-266), the Royal Society Wolfson Fellowship (RSWF/R3/183013), and the UK EPSRC (Grant No. EP/T028106/1).

Robust and high-precision quantum control is crucial but challenging for scalable quantum computation and quantum information processing. Traditional adiabatic control suffers severe limitations on gate performance imposed by environmentally induced noise because of a quantum system's limited coherence time. In this work, we experimentally demonstrate an alternative approach {to quantum control} based on deep reinforcement learning (DRL) on a trapped $^{171}\mathrm{Yb}^{+}$ ion. In particular, we find that DRL leads to fast and robust {digital quantum operations with running time bounded by shortcuts to adiabaticity} (STA). Besides, we demonstrate that DRL's robustness against both Rabi and detuning errors can be achieved simultaneously without any input from STA. Our experiments reveal a general framework of digital quantum control, leading to a promising enhancement in quantum information processing., 9 pages, 7 figures with Supplementary Material

To determine cut-off points in auto-assessment questionnaires to predict the presence and extent of presbylarynx signs.This case control, prospective, observational, and cross-sectional study was carried out on consecutive subjects observed by Otorhinolaryngology, in a tertiary center, in 2020. Each subject underwent fiberoptic videolaryngoscopy with stroboscopy, and presbylarynx was considered when it was identified two or more of the following endoscopic findings: vocal fold bowing, prominence of vocal processes in abduction, and a spindle-shaped glottal gap. Each subject completed three questionnaires: the Voice Handicap Index (VHI), with 30 and 10 questions, and the "Screening for voice disorders in older adults questionnaire" (RAVI).The studied population included 174 Caucasian subjects (60 males; 114 females), with a mean age of 73.99 years (standard deviation = 6.37; range 65-95 years). Presbylarynx was identified in 71 patients (41%). Among patients with presbylarynx, a glottal gap was identified in 22 patients (31%). The mean score of VHI-30 between "no presbylarynx" and "presbylarynx" groups was statistically different (P0.001), with a higher score for subjects with signs of presbylarynx. The presence of glottal gap was associated to a higher mean score of VHI-30 (41.64 ± 11.87) (P0.001). The mean score of VHI-10 between "no presbylarynx" and "presbylarynx" groups was statistically different (P0.001), with a higher score for subjects with signs of presbylarynx. Among patients with presbylarynx, the presence of glottal gap was associated to higher mean score of VHI-10 (14.04 ± 3.91) (P0.001). There was a strong positive correlation between VHI-30 and VHI-10 (rs = 0.969; P0.001). The mean score of RAVI between "no presbylarynx" and "presbylarynx" groups was statistically different (P0.001), with a higher score for subjects with signs of presbylarynx. Among patients with presbylarynx, the presence of glottal gap was associated to a higher mean score of RAVI (11.68 ± 1.61) (P0.001). There was a strong positive correlation not only between RAVI and VHI-30 (rs = 0.922; P0.001), but also between RAVI and VHI-10 (rs = 0.906; P0.001). The optimal cut-off points to discriminate "no presbylarynx" from "presbylarynx", obtained by the Youden' index, were 3.5 for RAVI, 4.5 for VHI-30 and 1.5 for VHI-10. RAVI had the highest sensitivity and specificity. The optimal cut-off points to predict glottal gap, obtained by the Youden' index, were 9.5 for RAVI, 21 for VHI-30 and 7.5 for VHI-10.The optimal cut-off points do discriminate "no presbylarynx" from "presbylarynx" were 3.5 for RAVI, 4.5 for VHI-30 and 1.5 for VHI-10. RAVI had the highest sensitivity and specificity, probably because it was designed specifically for vocal complaints of the elderly. Among patients with presbylarynx, cut-off points of 9.5 for RAVI, 21 for VHI-30 and 7.5 for VHI-10 were determined to predict patients with and without glottal gap. It was found a strong positive correlation between RAVI, VHI-30 and VHI-10. Thus, VHI-10 can be preferred to VHI-30 to assess voice impairment in clinical practice, because for elderly patients it is easier to answer. However, to predict endoscopic signs of presbylarynx, RAVI should be preferred.

8 pags., 5 figs., The quantum perceptron is a fundamental building block for quantum machine learning. This is a multidisciplinary feld that incorporates abilities of quantum computing, such as state superposition and entanglement, to classical machine learning schemes. Motivated by the techniques of shortcuts to adiabaticity, we propose a speed-up quantum perceptron where a control feld on the perceptron is inversely engineered leading to a rapid nonlinear response with a sigmoid activation function. This results in faster overall perceptron performance compared to quasi-adiabatic protocols, as well as in enhanced robustness against imperfections in the controls., We acknowledge fnancial support from Spanish Government via PGC2018-095113-B-I00 (MCIU/AEI/FEDER, UE), Basque Government via IT986-16, as well as from QMiCS (820505) and OpenSuperQ (820363) of the EU Flagship on Quantum Technologies, and the EU FET Open Grant Quromorphic (828826). J. C. acknowledges the Ramón y Cajal program (RYC2018- 025197-I) and the EUR2020-112117 Project of the Spanish MICINN,as well as support from the UPV/EHU through the Grant EHUrOPE. X. C. acknowledges NSFC (12075145), SMSTC (2019SHZDZX01-ZX04, 18010500400 and 18ZR1415500), the Program for Eastern Scholar and the Ramón y Cajal program of the Spanish MICINN (RYC-2017-22482). E. T. acknowledges support from Project PGC2018-094792-B-I00 (MCIU/AEI/FEDER,UE), CSIC Research Platform PTI-001, and CAM/FEDER Project No. S2018/TCS-4342 (QUITEMAD-CM).

Introduction and Objective: Patients with anomalous coronary arteries arising from the opposite sinus of Valsalva (ACAOS), the left coronary artery (LCA) arising from the right sinus or the right coronary artery (RCA) from the left sinus with an interarterial course, may present from complete absence of symptoms to sudden cardiac death. Although there are guidelines on indications for surgery, controversy remains. Methods: A retrospective review was performed of all adult patients diagnosed with ACAOS in our hospital between 2007 and 2016. Demographic, clinical, perioperative and follow-up data were collected from clinical records and summarized. A review of the published literature was performed with special emphasis on clinical presentation, surgical indications and results. Results: Seven symptomatic patients underwent surgery (mean age 57.1±8.9 years, two male, five female); they recovered without complications and to date have had no recurrence of myocardial ischemia. One asymptomatic patient with an anomalous RCA has been medically followed without evidence of myocardial ischemia. A 75-year-old woman, diagnosed in 2008 with an anomalous LCA, was not referred for surgery and died suddenly six months after diagnosis. Conclusions: Surgery for coronary abnormalities is performed with low risk and all published series report full operative survival. The indications for surgery are well established for patients with interarterial anomalous LCA and symptomatic patients with interarterial anomalous RCA. However, there is some uncertainty concerning asymptomatic patients, particularly those with an anomalous interarterial RCA, for whom we propose a more assertive approach, if young or engaged in strenuous activities. Resumo: Introdução e objetivo: Doentes com origem anómala de uma artéria coronária no seio coronário oposto (OAAC – artéria coronária esquerda, ACE, proveniente do seio direito ou artéria coronária direita, ACD, originária do seio esquerdo) com um percurso interarterial podem apresentar desde ausência de sintomas até morte súbita. Apesar da existência de guidelines para orientação cirúrgica, controvérsias persistem. Métodos: Foi feito um estudo retrospetivo de todos os doentes adultos diagnosticados com OAAC no Hospital de S. João, entre 2007 e 2016. Foram recolhidos dados demográficos, clínicos, perioperatórios e do seguimento. Uma revisão da literatura foi feita, enfatizou a apresentação clínica, as indicações e os resultados cirúrgicos. Resultados: Sete doentes sintomáticos foram submetidos a cirurgia (a média de idade foi de 57,1 ± 8,9 anos; dois homens, cinco mulheres), recuperaram sem complicações e sem recorrência de isquemia do miocárdio. Uma doente jovem assintomática, com uma ACD anómala, mantém-se em seguimento, sem intervenção e sem evidência de isquemia. O primeiro doente da série, sexo feminino, 75 anos, foi diagnosticada em 2008 com ACE anómala, não foi proposta para cirurgia e morreu subitamente seis meses após o diagnóstico. Conclusões: A cirurgia das anomalias coronárias é feita com risco baixo e sem mortalidade operatória em todas as séries publicadas. As indicações para cirurgia estão bem estabelecidas para doentes com ACE anómala e trajeto interarterial e em doentes sintomáticos com ACD anómala. Contudo, permanecem incertezas em doentes assintomáticos, particularmente naqueles que apresentam uma ACD anómala com trajeto interarterial, para os quais propomos uma abordagem mais interventiva, se jovens ou sujeitos a atividades vigorosas. Keywords: Anomalous aortic origin of the coronary artery, Sinus of Valsalva, Interarterial course, Cardiac surgery, Palavras-chave: Origem aórtica anómala da artéria coronária, Seio de Valsalva, Trajeto interarterial, Cirurgia cardíaca

Background: In Pediatric Otolaryngology surgery associating procedures is a common finding. Each surgical act elicits different degrees of pain, with implications on recovery. The aim of this work was to evaluate the severity of children's pain after outpatient surgery, considering combinations of common Otolaryngologic procedures.Methods: Data from children submitted to surgery in the Pediatric ambulatory Unit of Centro Hospitalar Universitário do Porto was reviewed. Children with history of previous interventions or any associated comorbidity were excluded. Postoperative pain at hospital discharge using the Universal Pain assessment tool (0-10) was assessed and compared concerning the various procedures.Results: A total of 954 operated children were included. Adenoidectomy was performed in 783 patients (82.1%), tonsillectomy in 714 (74.8%), myringotomy in 432 (45.3%) and radiofrequency inferior turbinoplasty in 98 (10.3%). Patients undergoing tonsillectomy showed significantly higher pain scores (1.48±1.02 in tonsillectomy versus 0.89±0.75 in no tonsillectomy, p=0.001). Importantly, adenoid curettage, radiofrequency inferior turbinoplasty and myringotomy did not associate with increased post-operative pain (p>0.05). Number of procedures within the same intervention and surgical indication (recurrent infections, obstructive sleep disordered breathing and otitis media with effusion) did not influence post-operative pain scores (p>0.05).Conclusions: Performing total tonsillectomy was the most important influencer of post-operative pain in Pediatric ambulatory surgery in this cohort. Performing concomitant adenoidectomy, turbinoplasty or miringotomy do not seem to influence post-operative pain significantly. A higher number of procedures within the same intervention does not associate directly with postoperative pain scores.

A 2-month-old infant with pulmonary atresia, ventricular septal defect, and major aortopulmonary collateral arteries developed an aneurysmatic elongation of the tricuspid valve tissue that partially closed and dynamically protruded through the ventricular septal defect, beneath the aortic valve. This rare finding caused dynamic left ventricle outflow tract obstruction and recurrent cardiac arrests and ultimately required surgical intervention.

Lung herniation is an uncommon entity which was fully classified in 1845 after the study of several case reports. Acquired lung hernia, especially traumatic, is the most common etiology. In the absence of clear guidelines, management of lung hernia is made in a case-by-case basis. We present an asymptomatic middle lobe hernia perceptible on physical examination, but diagnosed initially by imaging studies. Patient medical history included a blunt bull trauma fourteen years before.

Pulmonary sequestration (PS) is a rare congenital malformation, even more when its arterial supply is a coronary artery. We present a case of a 68-year-old man admitted in the emergency room with an acute coronary syndrome and no evidence of significant coronary disease. Instead, he had an abnormal branch from the circumflex coronary artery nourishing a mass in the left lower pulmonary lobe. A coronary steal phenomenon was proposed to explain the clinical presentation. An anterior left thoracotomy with ligation of the abnormal branch and atypical resection of the lung segment comprising the sequestration was performed.

We present a protocol for designing appropriately extended $\pi$ pulses that achieves tunable, thus selective, electron-nuclear spin interactions with low-driving radiation power. Our method is general since it can be applied to different quantum sensor devices such as nitrogen vacancy centers or silicon vacancy centers. Furthermore, it can be directly incorporated in commonly used stroboscopic dynamical decoupling techniques to achieve enhanced nuclear selectivity and control, which demonstrates its flexibility., Comment: 5 pages, 2 figures + Supplemental Material

The paradigmatic spin-boson model considers a spin degree of freedom interacting with an environment typically constituted by a continuum of bosonic modes. This ubiquitous model is of relevance in a number of physical systems where, in general, one has neither control over the bosonic modes, nor the ability to tune distinct interaction mechanisms. Despite this apparent lack of control, we present a suitable transformation that approximately maps the spin-boson dynamics into that of a tunable multiphoton Jaynes-Cummings model undergoing dissipation. Interestingly, the latter model describes the coherent interaction between a spin and a single bosonic mode via the simultaneous exchange of n bosons per spin excitation. Resorting to the so-called reaction coordinate method, we identify a relevant collective bosonic mode in the environment which is then used to generate multiphoton interactions following the proposed theoretical framework. Moreover, we show that spin-boson models featuring structured environments can lead into non-Markovian multiphoton Jaynes-Cummings dynamics. We discuss the validity of the proposed method depending on the parameters and analyze its performance, which is supported by numerical simulations. In this manner, the spin-boson model serves as a good analog quantum simulator for the inspection and realization of multiphoton Jaynes-Cummings models as well as the interplay of non-Markovian effects, and thus, as a simulator of light-matter systems with tunable interaction mechanisms., Comment: 12 pages, 4 figures; comments welcome!

Although most congenital coronary artery anomalies have no prognostic implications, associations with sudden cardiac death have been described, particularly in the young. We report an exercise-associated collapse in an otherwise asymptomatic middle-aged female marathoner. The aborted sudden cardiac death approach revealed an unexpected initial presentation of a malignant anomalous left main coronary artery origin, with ostial stenosis and interarterial course. The present case illustrates an unusually longstanding coexistence of a malignant anatomical variant with a persistent trigger.

Quantum field theories describe a variety of fundamental phenomena in physics. However, their study often involves cumbersome numerical simulations. Quantum simulators, on the other hand, may outperform classical computational capacities due to their potential scalability. Here we report an experimental realization of a quantum simulation of fermion–antifermion scattering mediated by bosonic modes, using a multilevel trapped ion, which is a simplified model of fermion scattering in both perturbative and non-perturbative quantum electrodynamics. The simulated model exhibits prototypical features in quantum field theory including particle pair creation and annihilation, as well as self-energy interactions. These are experimentally observed by manipulating four internal levels of a 171Yb+ trapped ion, where we encode the fermionic modes, and two motional degrees of freedom that simulate the bosonic modes. Our experiment establishes an avenue towards the efficient implementation of field modes, which may prove useful in studies of quantum field theories including non-perturbative regimes., Simulation of quantum field theory using quantum systems would in principle allow avoidance of the exponential overhead required for classical simulations. Here, the authors use a multilevel trapped ion to simulate the processes of self-interaction and particle-antiparticle creation/annihilation.

The realisation of optically detected magnetic resonance via nitrogen vacancy centers in diamond faces challenges at high magnetic fields which include growing energy consumption of control pulses as well as decreasing sensitivities. Here we address these challenges with the design of shaped pulses in microwave control sequences that achieve orders magnitude reductions in energy consumption and concomitant increases in sensitivity when compared to standard top-hat microwave pulses. The method proposed here is general and can be applied to any quantum sensor subjected to pulsed control sequences., Comment: 7 pages, 4 figures

Quantum simulation of complex quantum systems and their properties often requires the ability to prepare initial states in an eigenstate of the Hamiltonian to be simulated. In addition, to compute the eigenvalues of a Hamiltonian is in general a non-trivial problem. Here, we propose a hybrid quantum-classical probabilistic method to compute eigenvalues and prepare eigenstates of Hamiltonians which are simulatable with a trapped-ion quantum processor., Comment: 9 pages, 6 figures

We develop energy efficient, continuous microwave schemes to couple electron and nuclear spins, using phase or amplitude modulation to bridge their frequency difference. These controls have promising applications in biological systems, where microwave power should be limited, as well as in situations with high Larmor frequencies due to large magnetic fields and nuclear magnetic moments. These include nanoscale NMR where high magnetic fields achieves enhanced thermal nuclear polarization and larger chemical shifts. Our controls are also suitable for quantum information processors and nuclear polarization schemes., E. S. and J. C. acknowledge financial support from Spanish MINECO/FEDER FIS2015-69983-P, Basque Government IT986-16, as well as from QMiCS (820505) and OpenSuperQ (820363) of the EU Flagship on Quantum Technologies. J. C. acknowledges support by the Juan de la Cierva Grant No. IJCI-2016-29681. E. T. and J. J. G. R. acknowledge support from Spanish MINECO/FEDER Project No. FIS2015-70856-P, No. FIS2016-81891-REDT and CAMPRICYT ProjectQUITEMAD þ CMNo. S2013- ICE2801. M. B. P. acknowledges support by the ERC Synergy grant BioQ (Grant No. 319130), the EU project HYPERDIAMOND, the QuantERA project NanoSpin, the BMBF project DiaPol, the state of Baden-Württemberg through bwHPC, and the German Research Foundation (DFG) through Grant No. INST 40/467-1 FUGG. This material is also based upon work supported by the U.S. Department of Energy, Office of Science, Office of Advance Scientific Computing Research (ASCR), Quantum Algorithms Teams project under field work proposal ERKJ335.

We show that arbitrary $N$-qubit interactions among nuclear spins can be achieved efficiently in solid state quantum platforms, such as nitrogen vacancy centers in diamond, by exerting control only on the electron spin coupled to the nuclei. This allows to exploit nuclear spins as robust quantum registers and the direct measurement of nuclear many-body correlators. The method takes advantage of recently introduced dynamical decoupling techniques and avoids the necessity of external, slow, control on the nuclei. Our protocol is general, being applicable to other nuclear spin-based platforms with electronic spin defects acting as mediators as silicon carbide.

The nitrogen-vacancy (N-V) color center in diamond is an enormously important platform for the development of quantum sensors, including for single-spin and single-molecule NMR. Detection of weak single-spin signals is greatly enhanced by repeated sequences of microwave pulses; in these dynamicaldecoupling techniques, the key control parameters swept in the experiment are the time intervals, τ, between pulses. Here, we show that, in fact, the pulse duration tp offers a powerful additional control parameter. While a non-negligible tp was previously considered simply a source of experimental error, we elucidate here the underlying quantum dynamics: we identify a landscape of quantum-state crossings which are usually inactive (closed) but may be controllably activated (opened) by adjusting tp from zero. We identify these crossings with recently observed but unexpected dips (so-called spurious dips) seen in the quantum coherence of the N-V spin. With this new understanding, both the position and the strength of these sharp features may be accurately controlled; they coexist with the usual broader coherence dips of short-duration microwave pulses, but their sharpness allows for higher-resolution spectroscopy with quantum diamond sensors, or their analogs.

A hybrid quantum register consisting of nuclear spins in a solid-state platform coupled to a central electron spin is expected to combine the advantages of its elements. However, the potential to exploit long nuclear spin coherence times is severely limited by magnetic noise from the central electron spin during external interrogation. We overcome this obstacle and present protocols for addressing a decoherence-free nuclear spin subspace, which was not accessible by previously existing methods. We demonstrate the efficacy of our protocols using detailed numerical simulations of a nitrogen-vacancy centre with nearby $^{13}$C nuclei, and show that the resulting hybrid quantum register is immune to electron spin noise and external magnetic field drifts. Our work takes an important step toward realizing robust quantum registers that can be easily manipulated, entangled, and, at the same time, well isolated from external noise, with applications from quantum information processing and communication to quantum sensing., Comment: Revised version with more materials

The dynamics of the quantum Rabi model in the deep strong coupling regime is theoretically analyzed in a trapped-ion setup. Recognizably, the main hallmark of this regime is the emergence of collapses and revivals, whose faithful observation is hindered under realistic magnetic dephasing noise. Here we discuss how to attain a faithful implementation of the quantum Rabi model in the deep strong coupling regime which is robust against magnetic field fluctuations and at the same time provides a large tunability of the simulated parameters. This is achieved by combining standing wave laser configuration with continuous dynamical decoupling. In addition, we study the role that amplitude fluctuations play to correctly attain the quantum Rabi model using the proposed method. In this manner the present work further supports the suitability of continuous dynamical decoupling techniques in trapped-ion settings to faithfully realize different interacting dynamics., Comment: 9 pages, 3 figures

We present a method to identify spurious signals generated by finite-width pulses in quantum sensing experiments and apply it to recently proposed dynamical decoupling sequences for accurate spectral interpretation. We first study the origin of these fake resonances and quantify their behavior in a situation that involves the measurement of a classical magnetic field. Here we show that a change of the initial phase of the sensor or, equivalently, of the decoupling pulses leads to oscillations in the spurious signal intensity while the real resonances remain intact. Finally we extend our results to the quantum regime for the unambiguous detection of remote nuclear spins by utilization of a nitrogen vacancy sensor in diamond., Comment: 8 pages, 5 figures

We demonstrate that the quantum phase transition (QPT) of the Rabi model and critical dynamics near the QPT can be probed in the setup of a single trapped ion. We first show that there exists equilibrium and non-equilibrium universal functions of the Rabi model by finding a proper rescaling of the system parameters and observables. We then propose a scheme that can faithfully realize the Rabi model in the limit of a large ratio of the effective atomic transition frequency to the oscillator frequency using a single trapped-ion and therefore the QPT. It is demonstrated that the predicted universal functions can indeed be observed based on our scheme. Finally, the effects of realistic noise sources on probing the universal functions in experiments are examined., Main text: 5 pages, 3 figures; supplemental material: 6 pages, 4 figures

We propose a method to measure the hyperfine vectors between a nitrogen-vacancy (NV) center and an environment of interacting nuclear spins. Our protocol enables the generation of tunable electron-nuclear coupling Hamiltonians while suppressing unwanted inter-nuclear interactions. In this manner, each nucleus can be addressed and controlled individually thereby permitting the reconstruction of the individual hyperfine vectors. With this ability the 3D-structure of spin ensembles and spins in bio-molecules can be identified without the necessity of varying the direction of applied magnetic fields. We demonstrate examples including the complete reconstruction of an interacting spin cluster in diamond and 3D imaging of all the nuclear spins in a bio-molecule.