RESUMEN
To build a universal quantum computer from fragile physical qubits, effective implementation of quantum error correction (QEC)1 is an essential requirement and a central challenge. Existing demonstrations of QEC are based on an active schedule of error-syndrome measurements and adaptive recovery operations2,3,4,5,6,7 that are hardware intensive and prone to introducing and propagating errors. In principle, QEC can be realized autonomously and continuously by tailoring dissipation within the quantum system1,8,9,10,11,12,13,14, but so far it has remained challenging to achieve the specific form of dissipation required to counter the most prominent errors in a physical platform. Here we encode a logical qubit in Schrödinger cat-like multiphoton states15 of a superconducting cavity, and demonstrate a corrective dissipation process that stabilizes an error-syndrome operator: the photon number parity. Implemented with continuous-wave control fields only, this passive protocol protects the quantum information by autonomously correcting single-photon-loss errors and boosts the coherence time of the bosonic qubit by over a factor of two. Notably, QEC is realized in a modest hardware setup with neither high-fidelity readout nor fast digital feedback, in contrast to the technological sophistication required for prior QEC demonstrations. Compatible with additional phase-stabilization and fault-tolerant techniques16,17,18, our experiment suggests quantum dissipation engineering as a resource-efficient alternative or supplement to active QEC in future quantum computing architectures.
RESUMEN
BACKGROUND: Predictive models based on radiomics features are novel, highly promising approaches for gynaecological oncology. Here, we wish to assess the prognostic value of the newly discovered Radiomic Prognostic Vector (RPV) in an independent cohort of high-grade serous ovarian cancer (HGSOC) patients, treated within a Centre of Excellence, thus avoiding any bias in treatment quality. METHODS: RPV was calculated using standardised algorithms following segmentation of routine preoperative imaging of patients (n = 323) who underwent upfront debulking surgery (01/2011-07/2018). RPV was correlated with operability, survival and adjusted for well-established prognostic factors (age, postoperative residual disease, stage), and compared to previous validation models. RESULTS: The distribution of low, medium and high RPV scores was 54.2% (n = 175), 33.4% (n = 108) and 12.4% (n = 40) across the cohort, respectively. High RPV scores independently associated with significantly worse progression-free survival (PFS) (HR = 1.69; 95% CI:1.06-2.71; P = 0.038), even after adjusting for stage, age, performance status and residual disease. Moreover, lower RPV was significantly associated with total macroscopic tumour clearance (OR = 2.02; 95% CI:1.56-2.62; P = 0.00647). CONCLUSIONS: RPV was validated to independently identify those HGSOC patients who will not be operated tumour-free in an optimal setting, and those who will relapse early despite complete tumour clearance upfront. Further prospective, multicentre trials with a translational aspect are warranted for the incorporation of this radiomics approach into clinical routine.
Asunto(s)
Recurrencia Local de Neoplasia , Neoplasias Ováricas , Humanos , Recurrencia Local de Neoplasia/diagnóstico por imagen , Neoplasia Residual , Neoplasias Ováricas/diagnóstico por imagen , Neoplasias Ováricas/tratamiento farmacológico , Neoplasias Ováricas/cirugía , Pronóstico , Estudios RetrospectivosRESUMEN
BACKGROUND: Cardiophrenic lymph nodes (CPLN) define FIGO stage IVB disease. We evaluate the pattern of CPLN metastases, their prognostic impact and the potential role of CPLN resection in patients with epithelial ovarian cancer (EOC). METHODS: Analysis of 595 consecutive patients with EOC treated in the period 01/2011-05/2016. CT scans were re-reviewed by two radiologists. Positive CPLN were defined as ≥5â¯mm in the short-axis diameter. The role of CPLN resection was evaluated in a case-control matched-pair analysis. RESULTS: Of 595 patients 458 had FIGO stage IIIB-IV disease. We excluded patients undergoing interval surgery (nâ¯=â¯54), without debulking surgery (nâ¯=â¯32) and without sufficient pre-operative imaging (nâ¯=â¯22), resulting in a study cohort of 350 patients. Of these, 133 (37.9%) had negative CPLN and 217 (62.0%) had radiologically positive CPLN. In patients with postoperative residual tumor, enlarged CPLN had no impact on survival. In patients with complete resection (nâ¯=â¯223), 98 (44.0%) had negative CPLN and a 5-year OS of 69% and a 5-year PFS of 41%; in contrast, in the 125 patients (56.0%) with positive CPLN, 5-year OS was 30% and 5-year PFS was 13%. In 52 patients we resected CPLN. The matched-pair case-control analysis did not demonstrate any significant impact on survival of CPLN resection. CONCLUSION: CPLN metastases are associated with impaired PFS and OS in patients with macroscopically completely resected tumor. Intraabdominal residual tumor has a greater prognostic impact than positive CPLN. The impact of the resection of CPLN remains unclear.
Asunto(s)
Carcinoma Epitelial de Ovario/patología , Neoplasias Ováricas/patología , Carcinoma Epitelial de Ovario/mortalidad , Femenino , Humanos , Metástasis Linfática , Estadificación de Neoplasias , Neoplasias Ováricas/mortalidadRESUMEN
BACKGROUND: Sarcopenia was reported as a prognostic factor in cancer patients. Using computed tomography (CT), we analyzed the impact of sarcopenia on overall survival (OS) in patients with advanced epithelial ovarian cancer (EOC) after primary debulking surgery (PDS). METHODS: Preoperative CT scans of consecutive EOC patients (n = 323) were retrospectively assessed for skeletal muscle index (SMI) and muscle attenuation (MA; Hounsfield units [HU]). The optimal cut-off point for MA (32 HU) was calculated using the Martingale residuals method, and previously reported cut-offs for SMI were used. Logistic regression was used to determine univariate and multivariate factors associated with OS. RESULTS: Sarcopenia defined as SMI < 38.5, < 39, and 41 cm2/m2 was detected in 29.4, 33.7, and 47.1% of patients, respectively; however, none of these SMI cut-off levels were associated with OS. MA < 32 HU was present in 21.1% (68/323) of the total cohort. Significant differences between patients with MA < 32 and ≥ 32 HU were detected for median age (67 vs. 57 years), Eastern Cooperative Oncology Group (ECOG) > 0 (13.2 vs. 3.1%), comorbidity (age-adjusted Charlson Comorbidity Index [ACCI] ≥ 4; 36.8 vs. 13.3%), median body mass index (BMI; 27 vs. 24 kg/m2), International Federation of Gynecology and Obstetrics (FIGO) stage, histology (high-grade serous 95.6 vs. 84.7%), and complete resection (38.2 vs. 68.2%). MA < 32 HU remained a significant prognostic factor for OS in multivariate Cox regression analysis (hazard ratio 1.79, p = 0.003). Median OS in patients with MA < 32 HU versus MA ≥ 32 HU was 28 versus 56 months (p < 0.001). Furthermore, MA < 32 HU was significantly associated with OS in the prognostically poor population of patients with residual tumor (p = 0.015). CONCLUSIONS: Low MA was significantly associated with poor survival, especially in patients with residual tumor after PDS. MA assessment could be used for risk stratification after PDS.
Asunto(s)
Carcinoma Epitelial de Ovario/mortalidad , Procedimientos Quirúrgicos de Citorreducción/mortalidad , Músculo Esquelético/patología , Sarcopenia/mortalidad , Adulto , Anciano , Anciano de 80 o más Años , Índice de Masa Corporal , Carcinoma Epitelial de Ovario/patología , Carcinoma Epitelial de Ovario/cirugía , Procedimientos Quirúrgicos de Citorreducción/efectos adversos , Femenino , Estudios de Seguimiento , Humanos , Persona de Mediana Edad , Músculo Esquelético/cirugía , Pronóstico , Estudios Retrospectivos , Sarcopenia/etiología , Sarcopenia/patología , Tasa de Supervivencia , Adulto JovenRESUMEN
We realize a Λ system in a superconducting circuit, with metastable states exhibiting lifetimes up to 8 ms. We exponentially suppress the tunneling matrix elements involved in spontaneous energy relaxation by creating a "heavy" fluxonium, realized by adding a capacitive shunt to the original circuit design. The device allows for both cavity-assisted and direct fluorescent readouts, as well as state preparation schemes akin to optical pumping. Since direct transitions between the metastable states are strongly suppressed, we utilize Raman transitions for coherent manipulation of the states.
RESUMEN
We autonomously stabilize arbitrary states of a qubit through parametric modulation of the coupling between a fixed frequency qubit and resonator. The coupling modulation is achieved with a tunable coupling design, in which the qubit and the resonator are connected in parallel to a superconducting quantum interference device. This allows for quasistatic tuning of the qubit-cavity coupling strength from 12 MHz to more than 300 MHz. Additionally, the coupling can be dynamically modulated, allowing for single-photon exchange in 6 ns. Qubit coherence times exceeding 20 µs are maintained over the majority of the range of tuning, limited primarily by the Purcell effect. The parametric stabilization technique realized using the tunable coupler involves engineering the qubit bath through a combination of photon nonconserving sideband interactions realized by flux modulation, and direct qubit Rabi driving. We demonstrate that the qubit can be stabilized to arbitrary states on the Bloch sphere with a worst-case fidelity exceeding 80%.
RESUMEN
Superconducting circuits are promising candidates for constructing quantum bits (qubits) in a quantum computer; single-qubit operations are now routine, and several examples of two-qubit interactions and gates have been demonstrated. These experiments show that two nearby qubits can be readily coupled with local interactions. Performing gate operations between an arbitrary pair of distant qubits is highly desirable for any quantum computer architecture, but has not yet been demonstrated. An efficient way to achieve this goal is to couple the qubits to a 'quantum bus', which distributes quantum information among the qubits. Here we show the implementation of such a quantum bus, using microwave photons confined in a transmission line cavity, to couple two superconducting qubits on opposite sides of a chip. The interaction is mediated by the exchange of virtual rather than real photons, avoiding cavity-induced loss. Using fast control of the qubits to switch the coupling effectively on and off, we demonstrate coherent transfer of quantum states between the qubits. The cavity is also used to perform multiplexed control and measurement of the qubit states. This approach can be expanded to more than two qubits, and is an attractive architecture for quantum information processing on a chip.
RESUMEN
The choice of impedance used to shunt a Josephson junction determines if the charge transferred through the circuit is quantized: a capacitive shunt renders the charge discrete, whereas an inductive shunt gives continuous charge. This discrepancy leads to a paradox in the limit of large inductances L. We show that while the energy spectra of the capacitively and inductively shunted junction are vastly different, their high-frequency responses become identical for large L. Inductive shunting thus opens the possibility to observe charging effects unimpeded by charge noise.
RESUMEN
Successive multiple ionic-polymer layers (SMIL) coatings have been often used in capillary electrophoresis due to their simplicity to implement and regenerate. However, the performances of the separation are strongly dependent on the nature of the polyelectrolyte partners used to build the SMIL coating. In this work, we investigate new couples of polyelectrolytes that were not tested before: namely, polybrene (PB), quaternized diethylaminoethyl dextran (DEAEDq) and ε-poly(lysine) (ε-PLL), as polycations, in combination with poly(acrylic acid), dextran sulfate, poly(styrenesulfonate), poly(methacrylic acid) and poly(l-lysine citramide), as polyanions. Systematic study of intra- and inter-capillaries repeatabilities/reproducibilities was performed based on the determination of migration time, separation efficiency and electroosmotic mobility. Interestingly, the electroosmotic flow was found to vary with the nature of the polycation on a broad range of electroosmotic mobility decreasing in magnitude in the order of PB>ε-PLLâ¯>â¯DEAEDq, whatever the polyanion associated. Application of the coatings to the separation of proteins is illustrated in a 0.5â¯M acetic acid BGE, including CE-MS separation of ribonuclease B-glycoforms of the same mass (positional or structural isomers).
Asunto(s)
Electroósmosis/métodos , Electroforesis Capilar , Polielectrolitos/química , Proteínas/análisis , Proteínas/química , AnimalesRESUMEN
In the original version of this Article, the affiliation details for Peter Groszkowski and Jens Koch were incorrectly given as 'Department of Physics, University of Chicago, Chicago, IL, 60637, USA', instead of the correct 'Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA'. This has now been corrected in both the PDF and HTML versions of the Article.
RESUMEN
Qubit connectivity is an important property of a quantum processor, with an ideal processor having random access-the ability of arbitrary qubit pairs to interact directly. This a challenge with superconducting circuits, as state-of-the-art architectures rely on only nearest-neighbor coupling. Here, we implement a random access superconducting quantum information processor, demonstrating universal operations on a nine-qubit memory, with a Josephson junction transmon circuit serving as the central processor. The quantum memory uses the eigenmodes of a linear array of coupled superconducting resonators. We selectively stimulate vacuum Rabi oscillations between the transmon and individual eigenmodes through parametric flux modulation of the transmon frequency. Utilizing these oscillations, we perform a universal set of quantum gates on 38 arbitrary pairs of modes and prepare multimode entangled states, all using only two control lines. We thus achieve hardware-efficient random access multi-qubit control in an architecture compatible with long-lived microwave cavity-based quantum memories.
RESUMEN
The aim of this study was the development of a reliable and fast method to estimate total abdominal fat volumes (TAF) in diabetic subjects on the basis of T1-weighted MR images. Thirty-seven patients with diabetes were examined (age 48 +/- 13 y mean +/- SD). A semiautomated computer assisted software program was developed to quantify intraabdominal (IAF), subcutaneous (SCF), and total abdominal fat volumes (TAF). The variability of image analysis for fat measurements between two observers and within observers was assessed. Mean volumes (+/- SD) for IAF, SCF and TAF were 10.5 1 (+/- 5.0 1), 15.1 1 (+/-7.3 1) and 25.7 1 (+/-11.5 1), respectively. Inter- and intraobserver reliability was excellent (r = 0.999 to r = 1.0). Per patient, the analysis required nine minutes in addition to a scan duration of seven minutes. As this analytic method using T1-weighted MR images allows a fast and reliable quantification of TAF, IAF and SCF, it may serve as a valuable tool for respective studies in diabetic subjects.
Asunto(s)
Tejido Adiposo/patología , Diabetes Mellitus Tipo 2/patología , Imagen por Resonancia Magnética/métodos , Abdomen , Adulto , Anciano , Femenino , Humanos , Masculino , Persona de Mediana Edad , Fantasmas de Imagen , Reproducibilidad de los ResultadosRESUMEN
The exact treatment of Markovian open quantum systems, when based on numerical diagonalization of the Liouville super-operator or averaging over quantum trajectories, is severely limited by Hilbert space size. Perturbation theory, standard in the investigation of closed quantum systems, has remained much less developed for open quantum systems where a direct application to the Lindblad master equation is desirable. We present such a perturbative treatment which will be useful for an analytical understanding of open quantum systems and for numerical calculation of system observables which would otherwise be impractical.
RESUMEN
The promise of single Cooper-pair quantum circuits based on tunnel junctions for metrology and quantum information applications is severely limited by the influence of offset charges: random, slowly drifting microscopic charges inherent in many solid-state systems. By shunting a small junction with the Josephson kinetic inductance of a series array of large-capacitance tunnel junctions, thereby ensuring that all superconducting islands are connected to the circuit by at least one large junction, we have realized a new superconducting artificial atom that is totally insensitive to offset charges. Yet its energy levels manifest the anharmonic structure associated with single Cooper-pair effects, a useful component for solid-state quantum computation.
RESUMEN
We present measurements of single-qubit gate errors for a superconducting qubit. Results from quantum process tomography and randomized benchmarking are compared with gate errors obtained from a double pi pulse experiment. Randomized benchmarking reveals a minimum average gate error of 1.1+/-0.3% and a simple exponential dependence of fidelity on the number of gates. It shows that the limits on gate fidelity are primarily imposed by qubit decoherence, in agreement with theory.
RESUMEN
We study the Josephson effect in small one-dimensional (1D) Josephson junction arrays. For weak Josephson tunneling, topologically different regions in the charge-stability diagram generate distinct current-phase (I-phi) relationships. We present results for a three-junction system in the vicinity of charge-degeneracy lines and triple points. We explain the generalization to larger arrays, show that discontinuities of the I-phi relation at phase pi persist and that, at maximum degeneracy, the problem can be mapped to a tight-binding model providing analytical results for arbitrary system size.
RESUMEN
We present a detailed characterization of coherence in seven transmon qubits in a circuit QED architecture. We find that spontaneous emission rates are strongly influenced by far off-resonant modes of the cavity and can be understood within a semiclassical circuit model. A careful analysis of the spontaneous qubit decay into a microwave transmission-line cavity can accurately predict the qubit lifetimes over 2 orders of magnitude in time and more than an octave in frequency. Coherence times T1 and T_{2};{*} of more than a microsecond are reproducibly demonstrated.
RESUMEN
BACKGROUND: Bendamustine is an alkylating agent with hybrid activity and proven efficacy in small-cell lung cancer associated with a favorable toxicity rate. This phase II study of carboplatin/bendamustine was conducted to evaluate the efficacy of this combination in patients with extensive disease small-cell lung cancer (ED-SCLC). METHODS: Fifty-six untreated patients with ED-SCLC were enrolled. Their median age was 63 years. Sixty-seven percent of patients were male and 18% had a World Health Organization performance status of 2. Bendamustine was administered as a 30- to 60-minute infusion at a dose of 80 mg/m2 on days 1 and 2, and carboplatin was given at an area under the curve of 5 on day 1 of a 21-day cycle. RESULTS: Fifty-five patients were assessable for response and toxicity. The overall response rate was 72.7% (95% confidence interval: 59%-84%), with one complete remission (1.8%). The median time to progression was 5.2 months (95% confidence interval: 4.2-5.6). At the time of evaluation, 71% of the patients had died. The median survival time reached 8.3 months (95% confidence interval: 6.6-9.9). The major toxicity of this regimen was myelosuppression, including grade 3 or 4 neutropenia (46%), thrombopenia (26%), anemia (15%), and infections (11%). Toxic death was recorded in two patients (3.6%). CONCLUSIONS: The carboplatin/bendamustine regimen is a well-tolerated cytostatic combination in ED-SCLC with activity comparable with that of other platinum-based regimens. Further investigations, such as a phase III trial, are currently planned.
Asunto(s)
Protocolos de Quimioterapia Combinada Antineoplásica/administración & dosificación , Carcinoma de Pulmón de Células no Pequeñas/tratamiento farmacológico , Carcinoma de Pulmón de Células no Pequeñas/mortalidad , Neoplasias Pulmonares/tratamiento farmacológico , Neoplasias Pulmonares/mortalidad , Anciano , Protocolos de Quimioterapia Combinada Antineoplásica/efectos adversos , Clorhidrato de Bendamustina , Carboplatino/administración & dosificación , Carboplatino/efectos adversos , Carcinoma de Pulmón de Células no Pequeñas/patología , Intervalos de Confianza , Relación Dosis-Respuesta a Droga , Esquema de Medicación , Femenino , Estudios de Seguimiento , Humanos , Infusiones Intravenosas , Estimación de Kaplan-Meier , Neoplasias Pulmonares/patología , Masculino , Dosis Máxima Tolerada , Persona de Mediana Edad , Estadificación de Neoplasias , Compuestos de Mostaza Nitrogenada/administración & dosificación , Compuestos de Mostaza Nitrogenada/efectos adversos , Selección de Paciente , Probabilidad , Medición de RiesgoRESUMEN
By a polaronic energy shift, the effective charging energy of molecules can become negative, favoring ground states with even numbers of electrons. Here we show that charge transport through such molecules near ground-state degeneracies is dominated by tunneling of electron pairs which coexists with (featureless) single-electron cotunneling. Because of the restricted phase space for pair tunneling, the current-voltage characteristics exhibit striking differences from the conventional Coulomb blockade. In asymmetric junctions, pair tunneling can be used for gate-controlled current rectification and switching.