Engineering Pure Polarized Microwave Fields for Hyperfine Qubit Control

We present a microfabricated surface-electrode ion trap with a pair of integrated waveguides that generate a standing microwave field resonant with the 171 Yb + hyperfine qubit. The waveguides are engineered to position the wave antinode near the center of the trap, resulting in maximum field amplitude and uniformity along the trap axis. By calibrating the relative amplitudes and phases of the waveguide currents, we can control the polarization of the microwave field to reduce off-resonant coupling to undesired Zeeman sublevels. We demonstrate single-qubit π -rotations as fast as 1 μ s with less than 6% variation in Rabi frequency over an 800 μ m microwave interaction region. Fully compensating pulse sequences further improve the uniformity of X -gates across this interaction region.We present a microfabricated surface-electrode ion trap with a pair of integrated waveguides that generate a standing microwave field resonant with the 171 Yb + hyperfine qubit. The waveguides are engineered to position the wave antinode near the center of the trap, resulting in maximum field amplitude and uniformity along the trap axis. By calibrating the relative amplitudes and phases of the waveguide currents, we can control the polarization of the microwave field to reduce off-resonant coupling to undesired Zeeman sublevels. We demonstrate single-qubit π -rotations as fast as 1 μ s with less than 6% variation in Rabi frequency over an 800 μ m microwave interaction region. Fully compensating pulse sequences further improve the uniformity of X -gates across this interaction region.

arXiv:1304.6636New Journal of PhysicsAug 27, 201343 citations

Direct Microwave Synthesis for Superconducting Qubit Control

Guihem Ribeill, Diana Lee, Brian Donovan +3 more

Bulletin of the American Physical SocietyMar 7, 20180 citations

Polarization-insensitive state preparation for trapped-ion hyperfine qubits

A. D. Leu, Matthew C. Smith, Mario F. Gely +1 more

Quantum state preparation for trapped-ion qubits often relies on high-quality circularly polarized light, which may be difficult to achieve with chip-based integrated optics technology. We propose and implement a hybrid optical and microwave scheme for intermediate-field hyperfine qubits which instead relies on frequency selectivity. Experimentally, we achieve 99.94 % fidelity for linearly polarized ( σ + / σ − ) light, using Ca + 43 at 28.8 mT. We find that the fidelity remains above 99.8 % for a mixture of all polarizations ( σ + / σ − / π ) . We calculate that the method is capable of 99.99 % fidelity in Ca + 43 , and even higher fidelities in heavier ions such as Ba + 137 . Published by the American Physical Society 2024Quantum state preparation for trapped-ion qubits often relies on high-quality circularly polarized light, which may be difficult to achieve with chip-based integrated optics technology. We propose and implement a hybrid optical and microwave scheme for intermediate-field hyperfine qubits which instead relies on frequency selectivity. Experimentally, we achieve 99.94 % fidelity for linearly polarized ( σ + / σ − ) light, using Ca + 43 at 28.8 mT. We find that the fidelity remains above 99.8 % for a mixture of all polarizations ( σ + / σ − / π ) . We calculate that the method is capable of 99.99 % fidelity in Ca + 43 , and even higher fidelities in heavier ions such as Ba + 137 . Published by the American Physical Society 2024

arXiv:2406.14448Physical Review AOct 16, 20242 citations

Optimal coupling of HoW10 molecular magnets to superconducting circuits near spin clock transitions

Ignacio Gimeno, Víctor Rollano, David Zueco +11 more

A central goal in quantum technologies is to maximize $G{T}_{2}$ , where $G$ stands for the coupling of a qubit to control and readout signals and ${T}_{2}$ is the qubit's coherence time. This is challenging, as increasing $G$ (e.g., by coupling the qubit more strongly to external stimuli) often leads to deleterious effects on ${T}_{2}$ . Here, we study the coupling of pure and magnetically diluted crystals of ${\mathrm{Ho}\mathrm{W}}_{10}$ magnetic clusters to microwave superconducting coplanar waveguides. Absorption lines give a broadband picture of the magnetic energy level scheme and, in particular, confirm the existence of level anticrossings at equidistant magnetic fields determined by the combination of crystal field and hyperfine interactions. Such ``spin clock transitions'' are known to shield the electronic spins against magnetic field fluctuations. The analysis of the microwave transmission shows that the spin-photon coupling also becomes maximum at these transitions. The results show that engineering spin-clock states of molecular systems offers a promising strategy to combine sizable spin-photon interactions with a sufficient isolation from unwanted magnetic noise sources.A central goal in quantum technologies is to maximize $G{T}_{2}$, where $G$ stands for the coupling of a qubit to control and readout signals and ${T}_{2}$ is the qubit's coherence time. This is challenging, as increasing $G$ (e.g., by coupling the qubit more strongly to external stimuli) often leads to deleterious effects on ${T}_{2}$. Here, we study the coupling of pure and magnetically diluted crystals of ${\mathrm{Ho}\mathrm{W}}_{10}$ magnetic clusters to microwave superconducting coplanar waveguides. Absorption lines give a broadband picture of the magnetic energy level scheme and, in particular, confirm the existence of level anticrossings at equidistant magnetic fields determined by the combination of crystal field and hyperfine interactions. Such ``spin clock transitions'' are known to shield the electronic spins against magnetic field fluctuations. The analysis of the microwave transmission shows that the spin-photon coupling also becomes maximum at these transitions. The results show that engineering spin-clock states of molecular systems offers a promising strategy to combine sizable spin-photon interactions with a sufficient isolation from unwanted magnetic noise sources.

arXiv:1911.07541Physical Review AppliedOct 26, 202310 citations

Novel microwave readout for phase qubits

Shwetank Kumar, Matthias Steffen, Mary-Beth Rothwell +3 more

Bulletin of the American Physical SocietyMar 17, 20100 citations

A central goal in quantum technologies is to maximize

G{T}_{2}

, where

G

stands for the coupling of a qubit to control and readout signals and

{T}_{2}

is the qubit's coherence time. This is challenging, as increasing

G

(e.g., by coupling the qubit more strongly to external stimuli) often leads to deleterious effects on

{T}_{2}

. Here, we study the coupling of pure and magnetically diluted crystals of

{\mathrm{Ho}\mathrm{W}}_{10}

magnetic clusters to microwave superconducting coplanar waveguides. Absorption lines give a broadband picture of the magnetic energy level scheme and, in particular, confirm the existence of level anticrossings at equidistant magnetic fields determined by the combination of crystal field and hyperfine interactions. Such ``spin clock transitions'' are known to shield the electronic spins against magnetic field fluctuations. The analysis of the microwave transmission shows that the spin-photon coupling also becomes maximum at these transitions. The results show that engineering spin-clock states of molecular systems offers a promising strategy to combine sizable spin-photon interactions with a sufficient isolation from unwanted magnetic noise sources.