| 1. |
- Hoi, Io Chun, 1984, et al.
(författare)
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Giant Cross–Kerr Effect for Propagating Microwaves Induced by an Artificial Atom
- 2013
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 111:5, s. article nr. 053601-
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the effective interaction between two microwave fields, mediated by a transmon-type superconducting artificial atom which is strongly coupled to a coplanar transmission line. The interaction between the fields and atom produces an effective cross–Kerr coupling. We demonstrate average cross–Kerr phase shifts of up to 20 degrees per photon with both coherent microwave fields at the single-photon level. Our results provide an important step toward quantum applications with propagating microwave photons.
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| 2. |
- Lu, Yong, 1989, et al.
(författare)
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Quantum efficiency, purity and stability of a tunable, narrowband microwave single-photon source
- 2021
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Ingår i: npj Quantum Information. - : Springer Science and Business Media LLC. - 2056-6387. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate an on-demand source of microwave single photons with 71–99% intrinsic quantum efficiency. The source is narrowband (300 kHz) and tuneable over a 600 MHz range around 5.2 GHz. Such a device is an important element in numerous quantum technologies and applications. The device consists of a superconducting transmon qubit coupled to the open end of a transmission line. A π-pulse excites the qubit, which subsequently rapidly emits a single photon into the transmission line. A cancellation pulse then suppresses the reflected π-pulse by 33.5 dB, resulting in 0.005 photons leaking into the photon emission channel. We verify strong antibunching of the emitted photon field and determine its Wigner function. Non-radiative decay and 1/f flux noise both affect the quantum efficiency. We also study the device stability over time and identify uncorrelated discrete jumps of the pure dephasing rate at different qubit frequencies on a time scale of hours, which we attribute to independent two-level system defects in the device dielectrics, dispersively coupled to the qubit. Our single-photon source with only one input port is more compact and scalable compared to standard implementations.
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| 3. |
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| 4. |
- Henriksson, Jens, 1991, et al.
(författare)
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Performance analysis of out-of-distribution detection on trained neural networks
- 2020
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Ingår i: Information and Software Technology. - : Elsevier B.V.. - 0950-5849 .- 1873-6025.
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Tidskriftsartikel (refereegranskat)abstract
- Context: Deep Neural Networks (DNN) have shown great promise in various domains, for example to support pattern recognition in medical imagery. However, DNNs need to be tested for robustness before being deployed in safety critical applications. One common challenge occurs when the model is exposed to data samples outside of the training data domain, which can yield to outputs with high confidence despite no prior knowledge of the given input. Objective: The aim of this paper is to investigate how the performance of detecting out-of-distribution (OOD) samples changes for outlier detection methods (e.g., supervisors) when DNNs become better on training samples. Method: Supervisors are components aiming at detecting out-of-distribution samples for a DNN. The experimental setup in this work compares the performance of supervisors using metrics and datasets that reflect the most common setups in related works. Four different DNNs with three different supervisors are compared during different stages of training, to detect at what point during training the performance of the supervisors begins to deteriorate. Results: Found that the outlier detection performance of the supervisors increased as the accuracy of the underlying DNN improved. However, all supervisors showed a large variation in performance, even for variations of network parameters that marginally changed the model accuracy. The results showed that understanding the relationship between training results and supervisor performance is crucial to improve a model's robustness. Conclusion: Analyzing DNNs for robustness is a challenging task. Results showed that variations in model parameters that have small variations on model predictions can have a large impact on the out-of-distribution detection performance. This kind of behavior needs to be addressed when DNNs are part of a safety critical application and hence, the necessary safety argumentation for such systems need be structured accordingly.
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| 5. |
- Henriksson, Jens, 1991, et al.
(författare)
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Towards Structured Evaluation of Deep Neural Network Supervisors
- 2019
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Ingår i: Proceedings - 2019 IEEE International Conference on Artificial Intelligence Testing, AITest 2019. - New York : Institute of Electrical and Electronics Engineers Inc.. - 9781728104928 ; 1
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Konferensbidrag (refereegranskat)abstract
- Deep Neural Networks (DNN) have improved the quality of several non-safety related products in the past years. However, before DNNs should be deployed to safety-critical applications, their robustness needs to be systematically analyzed. A common challenge for DNNs occurs when input is dissimilar to the training set, which might lead to high confidence predictions despite proper knowledge of the input. Several previous studies have proposed to complement DNNs with a supervisor that detects when inputs are outside the scope of the network. Most of these supervisors, however, are developed and tested for a selected scenario using a specific performance metric. In this work, we emphasize the need to assess and compare the performance of supervisors in a structured way. We present a framework constituted by four datasets organized in six test cases combined with seven evaluation metrics. The test cases provide varying complexity and include data from publicly available sources as well as a novel dataset consisting of images from simulated driving scenarios. The latter we plan to make publicly available. Our framework can be used to support DNN supervisor evaluation, which in turn could be used to motive development, validation, and deployment of DNNs in safety-critical applications.
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| 6. |
- Pierre, Mathieu, 1983, et al.
(författare)
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Resonant and off-resonant microwave signal manipulation in coupled superconducting resonators
- 2019
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 99:9
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Tidskriftsartikel (refereegranskat)abstract
- We present an experimental demonstration as well as a theoretical model of an integrated circuit designed for the manipulation of a microwave field down to the single-photon level. The device is made of a superconducting resonator coupled to a transmission line via a second frequency-tunable resonator. The tunable resonator can be used as a tunable coupler between the fixed resonator and the transmission line. Moreover, the manipulation of the microwave field between the two resonators is possible. In particular, we demonstrate the swapping of the field from one resonator to the other by pulsing the frequency detuning between the two resonators. The behavior of the system, which determines how the device can be operated, is analyzed as a function of one key parameter of the system, the damping ratio of the coupled resonators. We show a good agreement between experiments and simulations, realized by solving a set of coupled differential equations.
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| 7. |
- Pierre, Mathieu, 1983, et al.
(författare)
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Storage and on-demand release of microwaves using superconducting resonators with tunable coupling
- 2014
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 104:23, s. Art. Nr. 232604-
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Tidskriftsartikel (refereegranskat)abstract
- We present a system which allows to tune the coupling between a superconducting resonator and a transmission line. This storage resonator is addressed through a second, coupling resonator, which is frequency-tunable and controlled by a magnetic flux applied to a superconducting quantum interference device. We experimentally demonstrate that the lifetime of the storage resonator can be tuned by more than three orders of magnitude. A field can be stored for 18 mu s when the coupling resonator is tuned off resonance and it can be released in 14 ns when the coupling resonator is tuned on resonance. The device allows capture, storage, and on-demand release of microwaves at a tunable rate.
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| 8. |
- Sathyamoorthy, Sankar Raman, 1984, et al.
(författare)
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Detecting itinerant single microwave photons
- 2016
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Ingår i: Comptes Rendus Physique. - : Elsevier BV. - 1878-1535 .- 1631-0705. ; 17:7, s. 756-765
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Single-photon detectors are fundamental tools of investigation in quantum optics and play a central role in measurement theory and quantum informatics. Photodetectors based on different technologies exist at optical frequencies and much effort is currently being spent on pushing their efficiencies to meet the demands coming from the quantum computing and quantum communication proposals. In the microwave regime, however, a single-photon detector has remained elusive, although several theoretical proposals have been put forth. In this article, we review these recent proposals, especially focusing on non-destructive detectors of propagating microwave photons. These detection schemes using superconducting artificial atoms can reach detection efficiencies of 90% with the existing technologies and are ripe for experimental investigations. (C) 2016 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
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| 9. |
- Sathyamoorthy, Sankar Raman, 1984
(författare)
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Engineering and detecting microwave photons
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Microwave quantum optics using superconducting circuits, also known as circuit QED, is a recent and promising field to study light-matter interactions at the fundamental level. In this field, artificial atoms made of superconducting elements interact with microwave photons routed through one dimensional transmission lines. This thesis is under the purview of circuit QED and is based on the three appended papers. In these three articles, we look at the problems of engineering photon-photon interaction (a la cross-Kerr effect) in microwaves using an artificial atom, storing and retrieving microwave photons using a tunable cavity and finally detecting a single propagating microwave photon non-destructively. The analysis is done using the framework of open quantum systems, where we use master equations and stochastic master equations to study the evolution of these artificial atoms in the presence of environment and under measurements respectively.
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| 10. |
- Sathyamoorthy, Sankar Raman, 1984, et al.
(författare)
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Quantum Nondemolition Detection of a Propagating Microwave Photon
- 2014
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 112:9, s. art. no. 093601-
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Tidskriftsartikel (refereegranskat)abstract
- The ability to nondestructively detect the presence of a single, traveling photon has been a long-standing goal in optics, with applications in quantum information and measurement. Realizing such a detector is complicated by the fact that photon-photon interactions are typically very weak. At microwave frequencies, very strong effective photon-photon interactions in a waveguide have recently been demonstrated. Here we show how this type of interaction can be used to realize a quantum nondemolition measurement of a single propagating microwave photon. The scheme we propose uses a chain of solid-state three-level systems (transmons) cascaded through circulators which suppress photon backscattering. Our theoretical analysis shows that microwave-photon detection with fidelity around 90% can be realized with existing technologies.
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