Nikos Daniilidis

Fabrication and heating rate study of microscopic surface electrode ion traps

We report heating rate measurements in a microfabricated gold- on-sapphire surface electrode ion trap with a trapping height of approximately 240µm. Using the Doppler recooling method, we characterize the trap heating rates over an extended region of the trap. The noise spectral density of the trap falls in the range of noise spectra reported in ion traps at room temperature. We find that during the first months of operation, the heating rates increase by approximately one order of magnitude. The increase in heating rates is largest in the ion-loading region of the trap, providing a strong hint that surface contamination plays a major role for excessive heating rates. We discuss data found in the literature and the possible relation of anomalous heating to sources of noise and dissipation in other systems, namely impurity atoms adsorbed onto metal surfaces and amorphous dielectrics.

Wiring up trapped ions to study aspects of quantum information

There has been much interest in developing methods for transferring quantum information. We discuss a way to transfer quantum information between two trapped ions through a wire. The motion of a trapped ion induces oscillating charges in the trap electrodes. By sending this current to the electrodes of a nearby second trap, the motions of ions in the two traps are coupled. We investigate the electrostatics of a setup where two separately trapped ions are coupled through an electrically floating wire. We also discuss experimental issues, including possible sources of decoherence.

Electric field compensation and sensing with a single ion in a planar trap

We use a single ion as a movable electric field sensor with accuracies on the order of a few V/m. For this, we compensate undesired static electric fields in a planar radio frequency trap and characterize the static field and its curvature over an extended region along the trap axis. We observe a strong buildup of stray charges around the loading region on the trap resulting in an electric field of up to 1.3 kV/m at the ion position. We also find that the profile of the stray field remains constant over a time span of a few months.

Cryogenic setup for trapped ion quantum computing

We report on the design of a cryogenic setup for trapped ion quantum computing containing a segmented surface electrode trap. The heat shield of our cryostat is designed to attenuate alternating magnetic field noise, resulting in 120 dB reduction of 50 Hz noise along the magnetic field axis. We combine this efficient magnetic shielding with high optical access required for single ion addressing as well as for efficient state detection by placing two lenses each with numerical aperture 0.23 inside the inner heat shield. The cryostat design incorporates vibration isolation to avoid decoherence of optical qubits due to the motion of the cryostat. We measure vibrations of the cryostat of less than ±20 nm over 2 s. In addition to the cryogenic apparatus, we describe the setup required for an operation with 40Ca+ and 88Sr+ ions. The instability of the laser manipulating the optical qubits in 40Ca+ is characterized by yielding a minimum of its Allan deviation of 2.4 ⋅ 10-15 at 0.33 s. To evaluate the performance of the apparatus, we trapped 40Ca+ ions, obtaining a heating rate of 2.14(16) phonons/s and a Gaussian decay of the Ramsey contrast with a 1/e-time of 18.2(8) ms.

Corrigendum: Fabrication and heating rate study of microscopic surface electrode ion traps

We report heating rate measurements in a microfabricated goldon-sapphire surface electrode ion trap with a trapping height of approximately 240 μm. Using the Doppler recooling method, we characterize the trap heating rates over an extended region of the trap. The noise spectral density of the trap falls in the range of noise spectra reported in ion traps at room temperature. We find that during the first months of operation, the heating rates increase by approximately one order of magnitude. The increase in heating rates is largest in the ion-loading region of the trap, providing a strong hint that surface contamination plays a major role for excessive heating rates. We discuss data found in the literature and the possible relation of anomalous heating to sources of noise and dissipation in other systems, namely impurity atoms adsorbed onto metal surfaces and amorphous dielectrics. 8 Author to whom any correspondence should be addressed. New Journal of Physics 13 (2011) 013032 1367-2630/11/013032+17

Transport of charged particles by adjusting rf voltage amplitudes

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Implications of surface noise for the motional coherence of trapped ions

We propose a planar architecture for scalable quantum information processing (QIP) that includes X-junctions through which particles can move without micromotion. This is achieved by adjusting radio frequency (rf) amplitudes to move an rf null along the legs of the junction. We provide a proof-of-principle by transporting dust particles in three dimensions via adjustable rf potentials in a 3D trap. For the proposed planar architecture, we use regularization techniques to obtain amplitude settings that guarantee smooth transport through the X-junction.

Two-mode coupling in a single-ion oscillator via parametric resonance

Electric noise from metallic surfaces is a major obstacle towards quantum applications with trapped ions due to motional heating of the ions. Here, we discuss how the same noise source can also lead to pure dephasing of motional quantum states. The mechanism is particularly relevant at small ion-surface distances, thus imposing a new constraint on trap miniaturization. By means of a free induction decay experiment, we measure the dephasing time of the motion of a single ion trapped 50~

Quantum information processing with trapped electrons and superconducting electronics

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Quantum Interfaces Between Atomic and Solid-State Systems

m above a Cu-Al surface. From the dephasing times we extract the integrated noise below the secular frequency of the ion. We find that none of the most commonly discussed surface noise models for ion traps describes both, the observed heating as well as the measured dephasing, satisfactorily. Thus, our measurements provide a benchmark for future models for the electric noise emitted by metallic surfaces.