Scaling up trapped-ion quantum computers requires new trap materials to be explored. Here we present experiments with a surface ion trap made from the high-temperature superconductor YBCO, a promising material for future trap designs. We show that voltage noise from superconducting electrode leads is negligible within the sensitivity ${S}_{V}=9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}20}\phantom{\rule{0.16em}{0ex}}{\mathrm{V}}^{2}/\mathrm{Hz}$ of our setup, and for lead dimensions typical for advanced trap designs. Furthermore, we investigate the frequency and temperature dependence of electric-field noise above a YBCO surface. We find a $1/f$ spectral dependence of the noise and a nontrivial temperature dependence, with a plateau in the noise stretching over roughly $60\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ . The onset of the plateau coincides with the superconducting transition, indicating a connection between the dominant noise and the YBCO trap material. We exclude the YBCO bulk as origin of the noise and suggest further experiments to decide between the two remaining options explaining the observed temperature dependence: noise screening within the superconducting phase, or surface noise activated by the YBCO bulk through some unknown mechanism.Scaling up trapped-ion quantum computers requires new trap materials to be explored. Here we present experiments with a surface ion trap made from the high-temperature superconductor YBCO, a promising material for future trap designs. We show that voltage noise from superconducting electrode leads is negligible within the sensitivity ${S}_{V}=9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}20}\phantom{\rule{0.16em}{0ex}}{\mathrm{V}}^{2}/\mathrm{Hz}$ of our setup, and for lead dimensions typical for advanced trap designs. Furthermore, we investigate the frequency and temperature dependence of electric-field noise above a YBCO surface. We find a $1/f$ spectral dependence of the noise and a nontrivial temperature dependence, with a plateau in the noise stretching over roughly $60\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. The onset of the plateau coincides with the superconducting transition, indicating a connection between the dominant noise and the YBCO trap material. We exclude the YBCO bulk as origin of the noise and suggest further experiments to decide between the two remaining options explaining the observed temperature dependence: noise screening within the superconducting phase, or surface noise activated by the YBCO bulk through some unknown mechanism.

arXiv:2106.03945Physical review. B./Physical review. BAug 27, 20215 citations

Cryogenic surface-electrode ion trap apparatus

T. Dubielzig, Martina Carsjens, M. Kohnen +2 more

Bulletin of the American Physical SocietyJun 4, 20140 citations

Superconducting NbTi Radiofrequency Resonator for Surface ion Traps

M. Schubert, D. Fegelein, Dominik Hanisch +3 more

Trapped-ion qubits are one approach among many for achieving scalable quantum computers. An ion trap has to be operated with several dc and radio frequency (rf) signals to trap and control its qubits. Many ion trap setups are operated at cryogenic temperatures to reduce thermal influences, to reach very high vacuum, and to achieve high fidelity for quantum operations. A resonance circuit, consisting of a coil and the capacitance of the trap electrodes, is used to step-up a low power rf signal to high amplitudes in close proximity to the ion trap. These ac fields are used to confine ions $70 \,{\rm \mu }\mathrm{m}$ above a surface ion trap chip. An increased quality factor (Q-factor) of the resonance circuit leads to a higher voltage gain, but the experiment also benefits from a better attenuation of parasitic frequency components in the confining electric field. The Q-factor is inversely proportional to the trap capacitance. Since ion traps are growing in size due to a larger number of qubits, the capacitance is increasing. Therefore, the development of a coil with low losses becomes even more important. In this work, we present the setup of a superconducting coil for a high-Q resonator, measurements of the Q-factor, and its temperature dependency. The coil is made of a niobium-titanium (NbTi) wire wound on a threaded bobbin made of ceramics and equipped with further thermalization structures. The superconducting resonator is a very promising approach to satisfy the needs for future trapped-ion quantum computing setups.Trapped-ion qubits are one approach among many for achieving scalable quantum computers. An ion trap has to be operated with several dc and radio frequency (rf) signals to trap and control its qubits. Many ion trap setups are operated at cryogenic temperatures to reduce thermal influences, to reach very high vacuum, and to achieve high fidelity for quantum operations. A resonance circuit, consisting of a coil and the capacitance of the trap electrodes, is used to step-up a low power rf signal to high amplitudes in close proximity to the ion trap. These ac fields are used to confine ions$70 \,{\rm \mu }\mathrm{m}$above a surface ion trap chip. An increased quality factor (Q-factor) of the resonance circuit leads to a higher voltage gain, but the experiment also benefits from a better attenuation of parasitic frequency components in the confining electric field. The Q-factor is inversely proportional to the trap capacitance. Since ion traps are growing in size due to a larger number of qubits, the capacitance is increasing. Therefore, the development of a coil with low losses becomes even more important. In this work, we present the setup of a superconducting coil for a high-Q resonator, measurements of the Q-factor, and its temperature dependency. The coil is made of a niobium-titanium (NbTi) wire wound on a threaded bobbin made of ceramics and equipped with further thermalization structures. The superconducting resonator is a very promising approach to satisfy the needs for future trapped-ion quantum computing setups.

IEEE Transactions on Applied SuperconductivityJan 8, 20240 citations

Coupling of ions to superconducting circuits

Sönke Möller, Nikos Daniilidis, Hartmut Häffner

Bulletin of the American Physical SocietyJun 6, 20130 citations

Observation of superconductivity and surface noise using a single trapped ion as a field probe

Kirill Lakhmanskiy, Philip C. Holz, Dominic Schärtl +5 more

Measuring and understanding electric-field noise from bulk material and surfaces is important for many areas of physics. In this work, we demonstrate the probing of electric-field noise from different sources with an ion, $225\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{m}$ above the trap surface. We detect noise levels as small as ${S}_{E}=5.2(11)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}\phantom{\rule{4pt}{0ex}}{\mathrm{V}}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}2}\phantom{\rule{0.16em}{0ex}}{\mathrm{Hz}}^{\ensuremath{-}1}$ at ${\ensuremath{\omega}}_{\text{z}}=2\ensuremath{\pi}\ifmmode\times\else\texttimes\fi{}1.51\phantom{\rule{4pt}{0ex}}\mathrm{MHz}$ and $T=12\phantom{\rule{4pt}{0ex}}\mathrm{K}$ . Our setup incorporates a controllable noise source utilizing a high-temperature superconductor. This element allows us, first, to benchmark and validate the sensitivity of our probe. Second, it allows us to probe noninvasively the bulk properties of the superconductor, observing a superconducting transition with an ion. For temperatures below the transition, we use our setup to assess different surface noise processes. The measured surface noise shows a deviation from a power law in the frequency domain. However, the temperature scaling of the data is not in a good agreement with existing surface noise models. Our results open perspectives for models in surface science and pave the way to test them experimentally.Measuring and understanding electric-field noise from bulk material and surfaces is important for many areas of physics. In this work, we demonstrate the probing of electric-field noise from different sources with an ion, $225\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{m}$ above the trap surface. We detect noise levels as small as ${S}_{E}=5.2(11)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}\phantom{\rule{4pt}{0ex}}{\mathrm{V}}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}2}\phantom{\rule{0.16em}{0ex}}{\mathrm{Hz}}^{\ensuremath{-}1}$ at ${\ensuremath{\omega}}_{\text{z}}=2\ensuremath{\pi}\ifmmode\times\else\texttimes\fi{}1.51\phantom{\rule{4pt}{0ex}}\mathrm{MHz}$ and $T=12\phantom{\rule{4pt}{0ex}}\mathrm{K}$. Our setup incorporates a controllable noise source utilizing a high-temperature superconductor. This element allows us, first, to benchmark and validate the sensitivity of our probe. Second, it allows us to probe noninvasively the bulk properties of the superconductor, observing a superconducting transition with an ion. For temperatures below the transition, we use our setup to assess different surface noise processes. The measured surface noise shows a deviation from a power law in the frequency domain. However, the temperature scaling of the data is not in a good agreement with existing surface noise models. Our results open perspectives for models in surface science and pave the way to test them experimentally.

arXiv:1805.00793Physical Review AFeb 4, 201918 citations

1/f

spectral dependence of the noise and a nontrivial temperature dependence, with a plateau in the noise stretching over roughly

60\phantom{\rule{0.16em}{0ex}}\mathrm{K}

. The onset of the plateau coincides with the superconducting transition, indicating a connection between the dominant noise and the YBCO trap material. We exclude the YBCO bulk as origin of the noise and suggest further experiments to decide between the two remaining options explaining the observed temperature dependence: noise screening within the superconducting phase, or surface noise activated by the YBCO bulk through some unknown mechanism.

70 \,{\rm \mu }\mathrm{m}

above a surface ion trap chip. An increased quality factor (Q-factor) of the resonance circuit leads to a higher voltage gain, but the experiment also benefits from a better attenuation of parasitic frequency components in the confining electric field. The Q-factor is inversely proportional to the trap capacitance. Since ion traps are growing in size due to a larger number of qubits, the capacitance is increasing. Therefore, the development of a coil with low losses becomes even more important. In this work, we present the setup of a superconducting coil for a high-Q resonator, measurements of the Q-factor, and its temperature dependency. The coil is made of a niobium-titanium (NbTi) wire wound on a threaded bobbin made of ceramics and equipped with further thermalization structures. The superconducting resonator is a very promising approach to satisfy the needs for future trapped-ion quantum computing setups.

T=12\phantom{\rule{4pt}{0ex}}\mathrm{K}

. Our setup incorporates a controllable noise source utilizing a high-temperature superconductor. This element allows us, first, to benchmark and validate the sensitivity of our probe. Second, it allows us to probe noninvasively the bulk properties of the superconductor, observing a superconducting transition with an ion. For temperatures below the transition, we use our setup to assess different surface noise processes. The measured surface noise shows a deviation from a power law in the frequency domain. However, the temperature scaling of the data is not in a good agreement with existing surface noise models. Our results open perspectives for models in surface science and pave the way to test them experimentally.