The generation and manipulation of ultracold atomic ensembles in the quantum regime require the application of dynamically controllable microwave fields with ultra-low noise performance. Here, we present a low-phase-noise microwave source with two independently controllable output paths. Both paths generate frequencies in the range of 6.835 GHz ± 25 MHz for hyperfine transitions in 87Rb. The presented microwave source combines two commercially available frequency synthesizers: an ultra-low-noise oscillator at 7 GHz and a direct digital synthesizer for radio frequencies. We demonstrate a low integrated phase noise of 480 µrad in the range of 10 Hz to 100 kHz and fast updates of frequency, amplitude, and phase in sub-µs time scales. The highly dynamic control enables the generation of shaped pulse forms and the deployment of composite pulses to suppress the influence of various noise sources.
The generation and manipulation of ultracold atomic ensembles in the quantum regime require the application of dynamically controllable microwave fields with ultra-low noise performance. Here, we present a low-phase-noise microwave source with two independently controllable output paths. Both paths generate frequencies in the range of 6.835 GHz ± 25 MHz for hyperfine transitions in 87Rb. The presented microwave source combines two commercially available frequency synthesizers: an ultra-low-noise oscillator at 7 GHz and a direct digital synthesizer for radio frequencies. We demonstrate a low integrated phase noise of 480 µrad in the range of 10 Hz to 100 kHz and fast updates of frequency, amplitude, and phase in sub-µs time scales. The highly dynamic control enables the generation of shaped pulse forms and the deployment of composite pulses to suppress the influence of various noise sources.
We describe and characterize a simple, low cost, low phase noise microwave source that operates near 6.800 GHz for agile, coherent manipulation of ensembles of (87)Rb. Low phase noise is achieved by directly multiplying a low phase noise 100 MHz crystal to 6.8 GHz using a nonlinear transmission line and filtering the output with custom band-pass filters. The fixed frequency signal is single sideband modulated with a direct digital synthesis frequency source to provide the desired phase, amplitude, and frequency control. Before modulation, the source has a single sideband phase noise near -140 dBc/Hz in the range of 10 kHz-1 MHz offset from the carrier frequency and -130 dBc/Hz after modulation. The resulting source is estimated to contribute added spin-noise variance 16 dB below the quantum projection noise level during quantum nondemolition measurements of the clock transition in an ensemble 7 × 10(5) (87)Rb atoms.
We present a radio frequency source based on the AD9914 direct digital synthesizer chip, with a frequency range up to 1.4 GHz. The phase noise at an output frequency of 1 GHz is lower than −110 dBc/Hz at a 10 kHz offset. Through an optimized design of a field-programmable gate array, we have achieved the theoretical maximum modulation rate of AD9914 and developed multiple functional modules for cold atom experiments to implement modulation of frequency, phase, and amplitude. The modulation update rate reaches 146 MHz. The phase modulation response latency is 158 ns, and the amplitude modulation response latency is 95.1 ns. We have applied the RF source to a sideband Pound–Drever–Hall locking experiment and achieved frequency stabilization, demonstrating its suitability for cold atom experiments that require precise and complex laser control.
We present a low-phase-noise microwave control system designed for spatial-domain atom interferometers, featuring the independent outputs of three microwave channels with minimal relative phase noise between them. Utilizing a nonlinear transmission line and single-sideband mixing with a digital signal source, we achieved three channels of 6835 MHz microwave frequency outputs, exhibiting absolute phase noises of −55, −100, and −124 dBc/Hz at 1 Hz, 1 kHz, and 1 MHz frequency offsets, respectively. We measured the relative phase noise between channels for a root mean square value of ∼251 μrad. A servo loop was integrated to stabilize the power ratio between Raman laser frequency components, ensuring long-term elimination of light shifts in the atom interferometer. The waveform parameters of the three microwave outputs can be adjusted independently, allowing for flexible manipulation of the atomic interference phase. These capabilities make the proposed microwave control system highly suitable for precise frequency and phase modulation in atom interferometer-based gyroscopes and accelerometers operating within continuous spatial-domain configurations.
A radio-frequency (RF) source designed for cold atom experiments is presented. The source uses AD9858, a direct digital synthesizer, to generate the sine wave directly, up to 400 MHz, with sub-Hz resolution. An amplitude control circuit consisting of wideband variable gain amplifier and high speed digital to analog converter is integrated into the source, capable of 70 dB off isolation and 4 ns on-off keying. A field programmable gate array is used to implement a versatile frequency and amplitude co-sweep logic. Owing to modular design, the RF sources have been used on many cold atom experiments to generate various complicated RF sequences, enriching the operation schemes of cold atoms, which cannot be done by standard RF source instruments.
Abstract Scaling superconducting quantum processors increasingly relies on custom control electronics that can simultaneously satisfy spectral purity, multi-channel isolation, and long-term stability within a compact and integrated platform. Here we present Quantum microwave source (QMW), a classical three-channel broadband low-noise microwave source that consolidates qubit XY drive, readout excitation, and Josephson parametric amplifier (JPA) pump generation onto a single hardware module operating from 4 to 14 GHz with an output power range of -20 to +10 dBm. Electronic characterization yields a spurious-free dynamic range greater than 55 dB, equivalently a largest spur below -55 dBc, a phase noise as low as -110 dBc/Hz at 10 kHz offset for a 5 GHz carrier and below -103 dBc/Hz at the same offset across the full band, and output power stability within 0.1 dB over 24 hours. Integrated into the control chain of a 36-qubit superconducting processor, QMW pumps a JPA to 19.2 dB gain to enable high-SNR single-shot readout, while sustaining qubit coherence times of T 1 = 60.1 ± 0.8 μs, T 2,Ramsey = 24.2 ± 1.5 μs, and T 2,echo = 58.6 ± 2.1 μs, and an average single-qubit gate fidelity of 99.95 ± 0.05% measured by randomized benchmarking. The compact and modular nature of QMW provides a scalable microwave generation solution for largescale superconducting quantum processors, with potential extensions to other quantum hardware platforms and precision measurement applications.
This thesis describes the design, construction, and testing of a radio frequency signal source for generating rapidly changing frequencies in a repeatable and phase continuous manner. The radio frequency (RF) signal is generated by a Direct Digital Synthesizer (DDS) which is controlled by a triggerable microprocessor unit which is itself remotely programmed through an Ethernet connection. Waveforms generated by the RF source can be used for direct RF evaporation or RF manipulation of magnetic trapping potentials for ultra-cold atoms on an atom chip. The ultimate objective of the project is to mix the RF signal with higher frequency carrier waves to generate microwaves for the manipulation of hyperfine states of ultra-cold atoms of potassium and rubidium.