| 1. |
- Tholén, Erik, et al.
(författare)
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Note : The intermodulation lockin analyzer
- 2011
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 82:2, s. 026109-
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Tidskriftsartikel (refereegranskat)abstract
- Nonlinear systems can be probed by driving them with two or more pure tones while measuring the intermodulation products of the drive tones in the response. We describe a digital lockin analyzer which is designed explicitly for this purpose. The analyzer is implemented on a field-programmable gate array, providing speed in analysis, real-time feedback, and stability in operation. The use of the analyzer is demonstrated for intermodulation atomic force microscopy. A generalization of the intermodulation spectral technique to arbitrary drive waveforms is discussed.
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| 2. |
- Andersson, Gustav, 1990, et al.
(författare)
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Squeezing and Multimode Entanglement of Surface Acoustic Wave Phonons
- 2022
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Ingår i: PRX Quantum. - 2691-3399. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Exploiting multiple modes in a quantum acoustic device could enable applications in quantum information in a hardware-efficient setup, including quantum simulation in a synthetic dimension and continuous-variable quantum computing with cluster states. We develop a multimode surface acoustic wave (SAW) resonator with a superconducting quantum interference device (SQUID) integrated in one of the Bragg reflectors. The interaction with the SQUID-shunted mirror gives rise to coupling between the more than 20 accessible resonator modes. We exploit this coupling to demonstrate two-mode squeezing of SAW phonons, as well as four-mode multipartite entanglement. Our results open avenues for continuous-variable quantum computing in a compact hybrid quantum system.
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| 3. |
- Andersson, Gustav, et al.
(författare)
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Squeezing and Multimode Entanglement of Surface Acoustic Wave Phonons
- 2022
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Ingår i: PRX Quantum. - : American Physical Society (APS). - 2691-3399. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Exploiting multiple modes in a quantum acoustic device could enable applications in quantum information in a hardware-efficient setup, including quantum simulation in a synthetic dimension and continuous-variable quantum computing with cluster states. We develop a multimode surface acoustic wave (SAW) resonator with a superconducting quantum interference device (SQUID) integrated in one of the Bragg reflectors. The interaction with the SQUID-shunted mirror gives rise to coupling between the more than 20 accessible resonator modes. We exploit this coupling to demonstrate two-mode squeezing of SAW phonons, as well as four-mode multipartite entanglement. Our results open avenues for continuous-variable quantum computing in a compact hybrid quantum system.
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| 4. |
- Ankel, Martin, 1996, et al.
(författare)
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Experimental Evaluation of Moving Target Compensation in High Time-Bandwidth Noise Radar
- 2023
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Ingår i: 20th European Radar Conference, EuRAD 2023. ; , s. 213-216
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Konferensbidrag (refereegranskat)abstract
- In this article, the effect a moving target has on the signal-to-interference-plus-noise-ratio (SINR) for high time-bandwidth noise radars is investigated. To compensate for cell migration we apply a computationally efficient stretch processing algorithm that is tailored for batched processing and suitable for implementation onto a real-time radar processor. The performance of the algorithm is studied using experimental data. In the experiment, pseudorandom noise, with a bandwidth of 100 MHz, is generated and transmitted in real-time. An unmanned aerial vehicle (UAV), flown at a speed of 11.5 m/s, is acting as a target. For an integration time of 1 s, the algorithm is shown to yield an increase in SINR of roughly 13 dB, compared to no compensation. It is also shown that coherent integration times of 2.5 s can be achieved.
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| 5. |
- Ankel, Martin, et al.
(författare)
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Experimental Evaluation of Moving Target Compensation in High Time-Bandwidth Noise Radar
- 2023
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Ingår i: Proceedings 20th European Radar Conference (EuRAD). - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 213-216
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Konferensbidrag (refereegranskat)abstract
- In this article, the effect a moving target has on the signal-to-interference-plus-noise-ratio (SINR) for high time-bandwidth noise radars is investigated. To compensate for cell migration we apply a computationally efficient stretch processing algorithm that is tailored for batched processing and suitable for implementation onto a real-time radar processor. The performance of the algorithm is studied using experimental data. In the experiment, pseudorandom noise, with a bandwidth of 100 MHz, is generated and transmitted in real-time. An unmanned aerial vehicle (UAV), flown at a speed of 11.5 m/s, is acting as a target. For an integration time of 1 s, the algorithm is shown to yield an increase in SINR of roughly 13 dB, compared to no compensation. It is also shown that coherent integration times of 2.5 s can be achieved.
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| 6. |
- Ankel, Martin, 1996, et al.
(författare)
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Implementation of a coherent real‐time noise radar system
- 2023
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Ingår i: IET radar, sonar & navigation. - : Institution of Engineering and Technology (IET). - 1751-8784 .- 1751-8792.
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Tidskriftsartikel (refereegranskat)abstract
- The utilisation of continuous random waveforms for radar, that is, noise radar, has been extensively studied as a candidate for low probability of intercept operation. However, compared with the more traditional pulse-Doppler radar, noise radar systems are significantly more complicated to implement, which is likely why few systems exist. If noise radar systems are to see the light of day, system design, implementation, limitations etc., must be investigated. Therefore, the authors examine and detail the implementation of a real-time noise radar system on a field programmable gate array. The system is capable of operating with 100% duty cycle, 200 MHz bandwidth, and 268 ms integration time while processing a range of about 8.5 km. Additionally, the system can perform real-time moving target compensation to reduce cell migration. System performance is primarily limited by the memory bandwidth of the off-chip dynamic random access memory.
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| 7. |
- Jolin, Shan Williams, et al.
(författare)
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Calibration of mixer amplitude and phase imbalance in superconducting circuits
- 2020
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 91:12
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Tidskriftsartikel (refereegranskat)abstract
- An important device for modulation and frequency translation in the field of circuit quantum electrodynamics is the in-phase and quadrature mixer, an analog component for which calibration is necessary to achieve optimal performance. In this paper, we introduce techniques originally developed for wireless communication applications to calibrate upconversion and downconversion mixers. A Kalman filter together with a controllable carrier frequency offset calibrates both mixers without removing them from the embedding measurement infrastructure. These techniques can be embedded into room temperature control electronics and hopefully find widespread use as circuit quantum electrodynamics devices continue to grow in complexity.
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| 8. |
- Jolin, Shan Williams, et al.
(författare)
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Multipartite entanglement in a microwave frequency comb
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Significant progress has been made with multipartite entanglement of discrete qubits, but continuous variable systems may provide a more scalable path toward entanglement of large ensembles. We demonstrate multipartite entanglement in a microwave frequency comb generated by a Josephson parametric amplifier subject to a bichromatic pump. We find 64 correlated modes in the transmission line using a multifrequency digital signal processing platform. Full inseparability is verified in a subset of seven modes. Our method can be expanded to generate even more entangled modes in the near future.
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| 9. |
- Jolin, Shan Williams, et al.
(författare)
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Multipartite Entanglement in a Microwave Frequency Comb
- 2023
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Ingår i: Physical Review Letters. - : American Physical Society (APS). - 0031-9007 .- 1079-7114. ; 130:12
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Tidskriftsartikel (refereegranskat)abstract
- Significant progress has been made with multipartite entanglement of discrete qubits, but continuous variable systems may provide a more scalable path toward entanglement of large ensembles. We demonstrate multipartite entanglement in a microwave frequency comb generated by a Josephson parametric amplifier subject to a bichromatic pump. We find 64 correlated modes in the transmission line using a multifrequency digital signal processing platform. Full inseparability is verified in a subset of seven modes. Our method can be expanded to generate even more entangled modes in the near future.
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| 10. |
- Jonsson, Robert, 1989, et al.
(författare)
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Experimental Analysis of a Clutter Suppression Algorithm for High Time-Bandwidth Noise Radar
- 2023
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Ingår i: Proceedings of the IEEE Radar Conference. - 2375-5318 .- 1097-5764.
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Konferensbidrag (refereegranskat)abstract
- Noise-like, continuous waveforms have several benefits for radar operation, such as low probability of interception/identification. However, the same types of waveforms come with a significant drawback because strong signals, e.g., ground clutter, produce a correlation noise floor (CNF) that masks all weak signals. In this article, we report on the implementation and performance of an efficient clutter suppression algorithm used to suppress strong clutter echoes and allow for the detection of weaker signals. The algorithm's performance is verified using an experimental system with a time-bandwidth product of 70 dB at a centre frequency of 1.3 GHz. Application of the algorithm suppresses the CNF by over 30 dB, allowing for the detection of an unmanned aerial vehicle (UAV).
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| 11. |
- Kudra, Marina, 1992, et al.
(författare)
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Robust Preparation of Wigner-Negative States with Optimized SNAP-Displacement Sequences
- 2022
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Ingår i: PRX Quantum. - : AMER PHYSICAL SOC. - 2691-3399. ; 3:3
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Tidskriftsartikel (refereegranskat)abstract
- Hosting nonclassical states of light in three-dimensional microwave cavities has emerged as a promising paradigm for continuous-variable quantum information processing. Here we experimentally demonstrate high-fidelity generation of a range of Wigner-negative states useful for quantum computation, such as Schrodinger-cat states, binomial states, Gottesman-Kitaev-Preskill states, as well as cubic phase states. The latter states have been long sought after in quantum optics and have never been achieved experimentally before. We use a sequence of interleaved selective number-dependent arbitrary phase (SNAP) gates and displacements. We optimize the state preparation in two steps. First we use a gradient-descent algorithm to optimize the parameters of the SNAP and displacement gates. Then we optimize the envelope of the pulses implementing the SNAP gates. Our results show that this way of creating highly nonclassical states in a harmonic oscillator is robust to fluctuations of the system parameters such as the qubit frequency and the dispersive shift.
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| 12. |
- Tholen, Mats O., et al.
(författare)
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Characterization and benchmarking of a phase-sensitive two-qubit gate using direct digital synthesis
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We implement an iSWAP gate with two transmon qubits using a flux-tunable coupler. Precise control of the relative phase of the qubit-control pulses and the parametric-coupler drive is achieved with a multi-channel instrument called Presto using direct digital synthesis (DDS), a promising technique for scaling up quantum systems. We describe the process of tuning and benchmarking the iSWAP gate, where the relative phase of the pulses is controlled via software. We perform the iSWAP gate in 290 ns, validate it with quantum-state tomography, and measure 2% error with interleaved randomized benchmarking.
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| 13. |
- Tholen, Mats O., et al.
(författare)
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Measurement and control of a superconducting quantum processor with a fully integrated radio-frequency system on a chip
- 2022
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 93:10, s. 104711-
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Tidskriftsartikel (refereegranskat)abstract
- We describe a digital microwave platform called Presto, designed for measurement and control of multiple quantum bits (qubits) and based on the third-generation radio-frequency system on a chip. Presto uses direct digital synthesis to create signals up to 9 GHz on 16 synchronous output ports, while synchronously analyzing responses on 16 input ports. Presto has 16 DC-bias outputs, four inputs and four outputs for digital triggers or markers, and two continuous-wave outputs for synthesizing frequencies up to 15 GHz. Scaling to a large number of qubits is enabled through deterministic synchronization of multiple Presto units. A Python application programming interface configures a firmware for synthesis and analysis of pulses, coordinated by an event sequencer. The analysis integrates template matching (matched filtering) and low-latency (184-254 ns) feedback to enable a wide range of multi-qubit experiments. We demonstrate Presto's capabilities with experiments on a sample consisting of two superconducting qubits connected via a flux-tunable coupler. We show single-shot readout and active reset of a single qubit; randomized benchmarking of single-qubit gates showing 99.972% fidelity, limited by the coherence time of the qubit; and calibration of a two-qubit iSWAP gate.
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