We present the design of a compact vacuum chamber for trapping and laser cooling of 27Al+ a 40Ca+ ions. The vacuum chamber has been designed to a compact size to achieve good optical access to the trapped ions and ultra-high vacuum in the chamber. In combination with the Helmholtz coils, saddle coils, and magnetic shielding is achieved a homogenous magnetic field in the ion trapping area. The presented apparatus will enable quantum experiments with single ions and also Coulomb crystals.
We present the design of a compact vacuum chamber for trapping and laser cooling of 27Al+ a 40Ca+ ions. The vacuum chamber has been designed to a compact size to achieve good optical access to the trapped ions and ultra-high vacuum in the chamber. In combination with the Helmholtz coils, saddle coils, and magnetic shielding is achieved a homogenous magnetic field in the ion trapping area. The presented apparatus will enable quantum experiments with single ions and also Coulomb crystals.
We present a design of a new compact vacuum chamber with an electrical trap for trapping and laser cooling of 40Ca+ and 27Al+ ions. The custom chamber was designed to a minimum dimension to achieve ultra-high vacuum environment and good optical access to trapped ions. Combining the shape of the electrical trap with intrinsic geometrical symmetry and the size of the viewports will allow maximum efficiency of fluorescence collection from ions. The setup is ready for ablation and loading of 40Ca+ and 27Al+ ions to deal with quantum logic experiments for optical clock operation. In combination with magnetic saddle coils, Helmholtz coil and external magnetic shielding made of mu-metal, we achieve a very homogeneous magnetic field in the ion trapping area. The main part of a chamber equipped with viewports is made of titanium to maintain this homogeneous magnetic field and suppress residual fields. The presented setup will allow quantum experiments with single ions and Coulomb crystals in a stable and homogeneous magnetic field, which is necessary for many-ions optical clock systems.
SummaryWe present our arrangement of new apparatus for trapping Ca+and Al+ions. The apparatus consists of a compact vacuum chamber, linear quadrupole trap, one pair of Helmholtz coils, two pairs of saddle coils, and a magnetic shield. The new design respects the requirement of the large optical access for laser beam integration, a homogeneous magnetic field in the position of the ion in the trapping area, and an ultra-high vacuum regime to avoid interactions between residual gas and ions. The new apparatus is designed in a way so that all important subparts can be changed easily and allow us to minimize the time when the inner parts are exposed to the air during a component exchange. All parts of the arrangement, including the quadrupole trap, have been designed and developed by the Institute of Scientific Instruments in Brno, Czech Republic.
We are developing a new experimental apparatus for laser cooling of trapped ions, focusing on high electric field homogeneity, modularity and small size. The apparatus allows measurements with Coulomb crystals and easy modification for different experiments. The high homogeneity trap is created by electrospinning, while the modularity allows for the exchange of key parts. By miniaturizing the dimensions, we achieve a larger numerical aperture of the lens and a reduction in the size of the magnetic shielding. This portable apparatus offers new possibilities for ion studies and is promising for applications in satellite systems and reconnaissance satellites.
We present the design and characterization of a cryogenic vacuum chamber incorporating mechanical isolation from vibrations, a high numerical-aperture in-vacuum imaging objective, in-vacuum magnetic shielding, and an antenna for global radio frequency manipulation of trapped ions. The cold shield near 4 K is mechanically referenced to an underlying optical table via thermally insulating supports and exhibits root mean square vibrations less than 7.61(4) nm. Using the in-vacuum objective, we can detect 397 nm photons from a trapped 40Ca+ ion with 1.77% efficiency and achieve 99.9963(4)% single-shot state-detection fidelity in 50 μs. To characterize the efficacy of the magnetic shields, we perform Ramsey experiments on the ground-state qubit and obtain a coherence time of 24(2) ms, which extends to 0.25(1) s with a single spin-echo pulse. XY4 and XY32 dynamical decoupling sequences driven via the radio frequency antenna extend the coherence to 0.72(2) and 0.81(3) s, respectively.
This thesis describes experimental work towards developing a trapped ion quantum information processor. An existing ion trap apparatus was capable of trapping and laser-cooling single ions or small ion strings of 40 Ca+, and had been used for studies of quantum jumps and natural lifetime measurements in Ca. This thesis describes improvements in this apparatus, which have allowed the stability and the flexibility of experimental control of the ions to be greatly increased. This enabled experiments to read out the spin state of a single trapped ion, and to load ions with isotope selectivity through photoionization. The optical systems were improved by installation of new lasers, optical reference cavities, and a system of acousto-optic modulators for laser intensity switching and frequency control. The photon counting for fluorescence detection was improved, and a new photon time-of-arrival correlation circuit developed. This has permitted rapid and more sensitive detection of micromotion, and hence cancellation of stray fields in the trap. A study of resonant circuits in the low RF, high voltage (10 MHz, 1 kV) regime was carried out with a view to developing a new RF supply for the Paul trap with reduced noise and increased power. A new supply based on a helical resonator was built and used to trap ions. This technique has reduced noise and will permit higher secular frequencies to be attained in the future. A magnetic field B in the ion trap is used to define a quantization axis, and in one series of experiments was required to be of order 100 G to provide a substantial Zeeman splitting. A set of magnetic field coils to control the size and direction of B is described. The design of these posed some problems owing to an unforseen issue with the vacuum chamber. In short, it is magnetizable and acts to first approximation like a magnetic shield. The field coils had to be sufficiently substantial to produce the desired field at the ion even in the presence of this shielding effect, and dark resonance (and other) spectra with Zeeman splitting were obtained to calibrate the field using the ion as a probe. Finally, the thesis describes the successful loading of the ion trap by laser photoionization from a weak atomic beam. This involved two new lasers at 423 nm and 389 nm. Saturated absorption spectroscopy of neutral calcium is first described, then transverse excitation of an atomic beam in our vacuum chamber is used to identify all the main isotopes of calcium and confirm their abundances in our source (a heated sample of natural calcium). Finally, photoionization is used to load the trap. This has three advantages over electron-impact ionization. By avoiding an electron gun, we avoid charging of insulating patches and subsequent electric field drift as they discharge; the flux in the atomic beam and hence calcium (and other) deposits on the electrodes can be greatly reduced; and most importantly, the photoionization is isotope selective. Evidence is presented which suggests that even with an non-enriched source, the rare isotope 43 Ca can be loaded with reasonable efficiency. This isotope is advantageous for quantum information experiments for several reasons, but chiefly because its ground state hyperfine structure can act as a stable qubit.
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.