A 750-mW, continuous-wave, solid-state laser source at 313 nm for cooling and manipulating trapped 9Be+ ions

Abstract

We present a solid-state laser system that generates 750 mW of continuous-wave single-frequency output at 313 nm. Sum-frequency generation with fiber lasers at 1550 nm and 1051 nm produces up to 2 W at 626 nm. This visible light is then converted to UV by cavity-enhanced second-harmonic generation. The laser output can be tuned over a 495 GHz range, which includes the 9 Be + laser cooling and repumping transitions. This is the first report of a narrow-linewidth laser system with sufficient power to perform fault-tolerant quantum-gate operations with trapped 9 Be + ions by use of stimulated Raman transitions. IntroductionTwo of the primary objectives in quantum information processing and computing, are scaling to large numbers of quantum gates, and achieving fault-tolerant gate operation [1][2]. A promising approach to achieving both objectives is to use trapped ions, in which the quantum information is encoded on internal atomic states [3]. Efforts to improve ion-trap scalability have focused on multizone arrays [4][5], with complex surface-electrode geometries that provide multiple trapping zones [6]. These traps include control electrodes that enable the shuttling of ions between zones that are used to perform gate operations, state detection, and information storage. For fault-tolerant two-qubit (quantum bit) gate operations, error-correction protocols have been proposed [7][8], but these require a sufficiently low error per gate (typically assumed to be less that 10 -4 ), and this threshold has not yet been achieved. In one approach, qubits are encoded into ground-state hyperfine states, since these are very well isolated from environmental effects that cause memory error. However, gate operations are usually performed via optical transitions with laser beams, leading to spontaneous emission that dominates gate error. Spontaneous emission is reduced by a large detuning from atomic resonance, but then higher laser powers required to maintain the gate speed. For example, Ozeri et al. calculate that with the commonly trapped ion species of 9 Be + , 25 Mg + , and 43 Ca + , in order to reach the fault-tolerant regime for a two-qubit phase gate, one needs narrow-linewidth, continuous-wave (cw) laser power in the range of 140 mW to 540 mW (and detuning from atomic resonance on the THz scale) [9].The most challenging aspect of developing laser sources for this purpose is that most of the wavelengths are in the UV region. For trapped 43 Ca + ions, the required 729 nm or 397 nm light can be generated directly with semiconductor lasers; but for the shorter wavelengths needed for most other trapped-ion species, the traditional approach has been to frequency-double the visible output from a ring dye laser. While solid-state lasers have replaced gas and dye lasers in many spectral regions, some wavelengths have remained difficult to produce. [11]. Their setup includes a frequencydoubled Nd:YAG laser at 532 nm, a titanium sapphire laser at 760 nm, and sum-frequency generation (SFG) in an enhancement cavity resona...

A simple 2 W continuous-wave laser system for trapping ultracold metastable helium atoms at the 319.8 nm magic wavelength

“…High power (several hundreds mW) was generated by sum frequency mixing and subsequent frequency doubling of two fiber lasers, retaining most of their high spatial and spectral mode quality [19][20][21]. Production of up to 2 W was demonstrated with such a system [20].…”

A high-power 626 nm diode laser system for Beryllium ion trapping

“…However, in cases where, e.g. Raman transitions are desired, higher optical powers are required [23], and the amount of available red light must be optimized. In the direct ECDL configuration we extract a few tens of mW from the main beamline for wavemeter measurement, Iodine spectroscopy, Fabry-Perot stabilization, etc., reducing the achievable UV output.…”

“…We have measured the instantaneous linewidth of the ECDL by performing a heterodyne interference experiment, comparing the ECDL against an independent source of 626 nm light derived from narrow-linewidth (∼100 kHz) fiber lasers and a nonlinear sum-frequency generation technique [23]. The instantaneous linewidth of the heterodyne beat note near 10 MHz was measured using a spectrum analyzer and found to be of order a few hundred kHz when the ECDL was operating near its maximum output power (∼180 mA drive current).…”

“…A traditional approach to generating the colors required * Present Address: Commonwealth Scientific and Industrial Research Organisation, Materials Science and Engineering, West Lindfield, NSW 2070, Australia † Electronic address: michael.biercuk@sydney.edu.au for experiments with 9 Be + has been to frequency double 100-500 mW red output from a ring dye laser operating near 626 nm. More recent work has seen the development of all-solid-state sources using infrared fiber lasers and nonlinear frequency conversion [20][21][22][23]. Both approaches, however, are costly and technically complex and a compact, economical alternative leveraging semiconductor diode lasers is highly desirable.…”

“…In this manuscript we describe the design and construction of a compact, economic external cavity diode laser (ECDL) system outputting 140 mW red light near 626 nm -sufficient for subsequent frequency doubling to produce ∼ 3 − 5 mW (∼70 mW red input to cavity after system losses) near 313nm using a home-built doubling cavity [23]. This work leverages recent advances in the production of high-power single-mode semiconductor laser diodes operating near 635nm which may be cryogenically cooled to shift their gain profiles near 626 nm at T ≈ −31…”