Highly frequency-stable lasers are ubiquitous tools for optical-frequency metrology, precision interferometry, and quantum information science. While making a universally applicable laser is unrealistic, spectral noise can be tailored for specific applications. Here we report a high-power 698-nm clock laser with a maximum output of 4W and minimized frequency noise up to a few kHz Fourier frequency, together with long-term instability of 3.5 × 10 − 17 at one to thousands of seconds. The laser-frequency noise is precisely characterized with atom-based spectral analysis that employs a pulse sequence designed to suppress sensitivity to intensity noise. This method provides universally applicable tunability of the spectral response and analysis of quantum sensors over a wide frequency range. With the optimized laser system characterized by this technique, we achieve an average single-qubit Clifford gate fidelity of up to F 1 2 = 0.999 64 ( 3 ) when simultaneously driving 3000 optical qubits with a homogeneous Rabi frequency ranging from 10 Hz to 1 kHz. This result represents the highest single optical-qubit-gate fidelity for a large number of atoms.
Highly frequency-stable lasers are ubiquitous tools for optical-frequency metrology, precision interferometry, and quantum information science. While making a universally applicable laser is unrealistic, spectral noise can be tailored for specific applications. Here we report a high-power 698-nm clock laser with a maximum output of 4W and minimized frequency noise up to a few kHz Fourier frequency, together with long-term instability of 3.5 × 10 − 17 at one to thousands of seconds. The laser-frequency noise is precisely characterized with atom-based spectral analysis that employs a pulse sequence designed to suppress sensitivity to intensity noise. This method provides universally applicable tunability of the spectral response and analysis of quantum sensors over a wide frequency range. With the optimized laser system characterized by this technique, we achieve an average single-qubit Clifford gate fidelity of up to F 1 2 = 0.999 64 ( 3 ) when simultaneously driving 3000 optical qubits with a homogeneous Rabi frequency ranging from 10 Hz to 1 kHz. This result represents the highest single optical-qubit-gate fidelity for a large number of atoms.
We propose and demonstrate an alternative method for spectral filtering and frequency stabilization of both 780-nm and 960-nm lasers using a high-finesse length-tunable cavity (HFLTC). Firstly, the length of HFLTC is stabilized to a commercial frequency reference. Then, the two lasers are locked to this HFLTC using the Pound–Drever–Hall (PDH) method which can narrow the linewidths and stabilize the frequencies of both lasers simultaneously. Finally, the transmitted lasers of HFLTC with each power up to about 100 μW, which act as seed lasers, are amplified using the injection locking method for single-atom Rydberg excitation. The linewidths of obtained lasers are narrowed to be less than 1 kHz, meanwhile the obtained lasers’ phase noise around 750 kHz are suppressed about 30 dB. With the spectrally filtered lasers, we demonstrate a Rabi oscillation between the ground state and Rydberg state of single-atoms in an optical trap tweezer with a decay time of (67 ± 37) μs, which is almost not affected by laser phase noise. We found that the maximum short-term laser frequency fluctuation of a single excitation lasers is at ∼3.3 kHz and the maximum long-term laser frequency drift of a single laser is ∼46 kHz during one month. Our work develops a stable and repeatable method to provide multiple laser sources of ultra-low phase noise, narrow linewidth, and excellent frequency stability, which is essential for high precision atomic experiments, such as neutral atom quantum computing, quantum simulation, quantum metrology, and so on.
Lasers with high spectral purity are indispensable for optical clocks and coherent manipulation of atomic and molecular qubits for applications such as quantum computing and quantum simulation. Stabilisation of the laser to a reference can provide a narrow linewidth and high spectral purity. However, widely-used diode lasers exhibit fast phase noise that prevents high fidelity qubit manipulation. Here we demonstrate a self-injection locked diode laser system utilizing a medium finesse cavity. The cavity not only provides a stable resonance frequency, but at the same time acts as a low-pass filter for phase noise beyond the cavity linewidth of around 100 kHz, resulting in low phase noise from dc to the injection lock limit. We model the expected laser performance and benchmark it using a single trapped 40Ca+-ion as a spectrum analyser. We show that the fast phase noise of the laser at relevant Fourier frequencies of 100 kHz to >2 MHz is suppressed to a noise floor of between -110 dBc/Hz and -120 dBc/Hz, an improvement of 20 to 30 dB over state-of-the-art Pound-Drever-Hall-stabilized extended-cavity diode lasers. This strong suppression avoids incoherent (spurious) spin flips during manipulation of optical qubits and improves laser-driven gates in using diode lasers with applications in quantum logic spectroscopy, quantum simulation and quantum computation.
Lasers with high spectral purity are indispensable for optical clocks and for the coherent manipulation of atomic and molecular qubits in applications such as quantum computing and quantum simulation. While the stabilization of such lasers to a reference can provide a narrow linewidth, the widely used diode lasers exhibit fast phase noise that prevents high-fidelity qubit manipulation. In this paper, we demonstrate a self-injection locked diode laser system that utilizes a high-finesse cavity. This cavity not only provides a stable resonance frequency, it also acts as a low-pass filter for phase noise beyond the cavity linewidth of around 100 kHz, resulting in low phase noise from dc to the injection lock limit. We model the expected laser performance and benchmark it using a single trapped 40 Ca + -ion as a spectrum analyzer. We show that the fast phase noise of the laser at relevant Fourier frequencies of 100 kHz to >2 MHz is suppressed to a noise floor of between −110 dBc/Hz and −120 dBc/Hz, an improvement of 20 to 30 dB over state-of-the-art Pound-Drever-Hall-stabilized extended-cavity diode lasers. This strong suppression avoids incoherent (spurious) spin flips during manipulation of optical qubits and improves laser-driven gates when using diode lasers in applications involving quantum logic spectroscopy, quantum simulation, and quantum computation.
We developed a fiber-laser-pumped Ti:sapphire laser system designed for quantum precision measurement applications. By employing a 35 W single-frequency 532 nm fiber laser as the pump source, the system delivered continuous-wave output powers of 4.12 W at 770.108 nm (D 1 line, K), 4.72 W at 780.244 nm (D 2 line, Rb), and 5.29 W at 794.982 nm (D 1 line, Rb), thereby fulfilling the requirements for optical pumping and probing of alkali atoms. To enhance frequency stability, saturated absorption spectroscopy was used to lock the laser frequency, resulting in frequency drifts below 1 MHz over two hours. Furthermore, since low-frequency intensity noise (DC-100 Hz) critically affects spin-relaxation-free quantum sensing, we carried out a theoretical analysis which identified the pump laser as the dominant noise source. By implementing feedback control to the pump source as well as an external noise suppression, both methods achieved over 30 dB of intensity noise suppression within the DC-4kHz frequency range. In addition, improved beam pointing stability further reduced noise below 3 Hz. These results collectively demonstrate the system’s strong potential for quantum sensing applications.
Atom interferometry on optical clock transitions is being pursued for numerous long-baseline experiments both terrestrially and for future space missions. Crucial to meeting these experiments' required sensitivities is the implementation of large momentum transfer ($>10^3\hbar k$). Here we show that to sequentially apply such a large momentum via π pulses places stringent requirements on the frequency noise of the interferometry laser, finding that the linewidth is required to be considerably lower than has previously been suggested. This is due to imperfect pulse fidelity in the presence of noise and is apparent even for an atom at rest interacting with resonant light, making this a fundamental constraint on operational fidelity for a given laser and pulse sequence. Within this framework, we further present and analyse two high-power, frequency-stabilised laser sources designed to perform interferometry on the 1S0 - 3P0 clock transitions of cadmium and strontium, respectively operating at 332 nm and 698 nm.
We demonstrate a straightforward frequency-locking technique that employs external modulation saturation absorption spectroscopy to achieve a high-performance 780 nm laser system. By externally modulating the laser frequency through a fiber electro-optic modulator, this scheme can stabilize multiple transitions of the 87Rb D2 line with excellent performance. Experimental results establish fractional frequency instability of 2.21 × 10-13 at 1 s with a linewidth of 1.46 kHz for the cycling transition 5S1/2(Fg = 2) → 5P3/2(Fe = 3). Notably, we have locked the system to the repumping transition 5S1/2(Fg = 1) → 5P3/2(Fe = 2), achieving a record-low instability of 1.98 × 10-12 at 1 s averaging time. This simplified laser system, featuring exceptional short-term frequency stability and multi-frequency locking capability, serves as a critical subsystem for the compact cold-atom optical clock, enabling advanced precision metrology applications. Furthermore, its metrological performance enables immediate applications in other quantum sensors, such as Rydberg electrometry, atomic magnetometry, and matter-wave interferometry.