An ultralow-noise superconducting radio-frequency ion trap for frequency metrology with highly charged ions

Abstract

We present a novel ultrastable superconducting radio-frequency (RF) ion trap realized as a combination of an RF cavity and a linear Paul trap. Its RF quadrupole mode at 34.52 MHz reaches a quality factor of Q ≈ 2.3 × 105 at a temperature of 4.1 K and is used to radially confine ions in an ultralow-noise pseudopotential. This concept is expected to strongly suppress motional heating rates and related frequency shifts that limit the ultimate accuracy achieved in advanced ion traps for frequency metrology. Running with its low-vibration cryogenic cooling system, electron-beam ion trap, and deceleration beamline supplying highly charged ions (HCIs), the superconducting trap offers ideal conditions for optical frequency metrology with ionic species. We report its proof-of-principle operation as a quadrupole-mass filter with HCIs and trapping of Doppler-cooled 9Be+ Coulomb crystals.

Material-Inherent Noise Sources in Quantum Information Architecture

“…Furthermore, in principle, the resistive loss in metal electrodes can be removed by using superconductors whose resistance is 0 below a critical phase transition temperature. A couple of research groups have fabricated high-temperature superconducting ion traps and scrutinized their electric field noise carefully [ 163 , 164 ]. While the resistance-induced electric field noise is suppressed in superconducting materials such as niobium [ 160 ] or high-temperature superconductors of yttrium barium copper oxide (YBCO) [ 163 ], there are still remaining noise sources on their surfaces.…”

Sympathetically cooled highly charged ions in a radio-frequency trap with superconducting magnetic shielding

“…To reduce these and minimize systematic frequency shifts, we developed a novel type of RF ion trap, CryPTEx-SC (Cryogenic Paul Trap Experiment-Superconducting). 36 It comprises a quasi-monolithic superconducting RF resonator with a built-in linear quadrupole trap, which filters the RF drive, shields magnetic field fluctuations, "freezes" the static field present at the onset of superconductivity, and enables coherent operations without the need for external fields and their stabilization.…”

“…CryPTEx-SC combines a quasi-monolithic superconducting RF resonator with a linear Paul trap and is described in detail elsewhere. 36 With a loaded quality factor of Q ≈ 3 × 10 4 , the niobium RF resonator works as a band-pass filter around the trap drive frequency Ω RF = 2π × 34.3 MHz. This suppresses RF noise at the sidebands Ω RF ± ωi due to the secular frequencies ωi of ions in the trap, which are induced by the RF drive and lead to motional heating of the ions.…”

“…An antenna inserted into the niobium resonator 36 sends microwaves for driving the Be + 2 S 1/2 (F = 1) ↔ (F = 2) transition at 1.25 GHz (see Fig. 12).…”

“…We now investigate how efficiently the superconducting resonator shields the trapped ions from environmental magnetic noise. Our outermost shielding within the vacuum chamber consists of nested OFHC (oxygen-free high conductivity) copper heat shields 36 that are nearly identical to those of the sister experiment 20,47 at Physikalisch-Technische Bundesanstalt (PTB), Braunschweig. These shields filter magnetic field noise above corner frequencies of 0.14-0.30 Hz along different axes by inducing counteracting eddy currents, as characterized in the PTB trap.…”