Individual addressing of ions using magnetic field gradients in a surface-electrode ion trap

Abstract

Dense array of ions in microfabricated traps represent one possible way to scale up ion trap quantum computing. The ability to address individual ions is an important component of such a scheme. We demonstrate individual addressing of trapped ions in a microfabricated surface-electrode trap using a magnetic field gradient generated on-chip. A frequency splitting of 310(2) kHz for two ions separated by 5 µm is achieved. Selective single qubit operations are performed on one of two trapped ions with an average of 2.2±1.0% crosstalk. Coherence time as measured by the spin-echo technique is unaffected by the field gradient.Trapped ion systems are promising candidates for implementing quantum computation [1]. Significant progress has been made in realizing quantum operations using a small number of ions as qubits [2,3,4,5,6]. Meaningful quantum computation involves a large number of qubits, and one possible way to scale up ion traps is to create a dense array of ions in microfabricated traps. The ability to individually address ions is an essential component of such a system. In this letter, we report the successful demonstration of individual addressing of single trapped ions in a linear crystal, using a magnetic field gradient generated in a microfabricated surface-electrode trap.Previous methods of individual ion addressing have included spatial and frequency separation. An example of spatial separation is the use of precisely focused laser beams aimed at only one ion at a time [7], which poses a significant technical challenge in laser beam control. Another approach is to transport ions between trap zones using varying DC potentials [4,8], which requires precision voltage and timing control. Separation in frequency space has been proposed and implemented by creating AC stark shifts using a far off-resonant laser [9,10]. Frequency selectivity can also be achieved by applying an inhomogeneous magnetic field gradient for spatiallyseparated ions [11]. This has been demonstrated in a linear Paul trap using hyperfine states of trapped 172 Yb + ions probed with rf radiation [12], and with neutral Cs atoms in an optical dipole trap [13]. A similar technique can be applied to magnetic-field-sensitive qubit transitions in the optical range. Such an approach requires separating the ion frequencies by much more than the desired gate speed [1].Here, we present the first design and implementation of a microfabricated trap to perform individual addressing for optical transitions using a magnetic field gradient. Addressability is demonstrated by observing distinct peaks in the frequency spectrum, and by performing Rabi oscillations on one of two trapped ions with a low probability of unwanted excitation on the neighbouring ion. Integrating the gradient-generating wires with microfabricated traps assures position stability. We evaluate this individual addressing scheme to show that we can achieve reasonable gate speeds, and minimal crosstalk between neighbouring ions, with no decrease in coherence time measured with spin-echo. Fi...

Addressing Two-Level Systems Variably Coupled to an Oscillating Field

“…This is an important figure of merit since small splittings require correspondingly longer pulses in order to frequency resolve the peaks. Comparing to the method of individual addressing using magnetic field gradients [10,11], the maximum splitting that we reached, of about 10 kHz, corresponds to a magnetic field gradient of about 50 G=cm (assuming a magnetic field sensitivity of 2:8 MHz=G), which is similar to the one obtained in [11]. The Rabi frequency for each ion is easily deduced from a spectrum such as Fig.…”

Universal gate-set for trapped-ion qubits using a narrow linewidth diode laser

“…Having a residual asymmetric detuning of less than 1 kHz modified the two curves but still allows the process to converge although to slightly different values. Figure 14(a) Using the maximum likelihood method to fit the data in figure 14(b), we conclude gate fidelity 3 of F = 0.985 (10). While part (≈5×10 −3 ) of the gate error can be attributed to imperfection in the preparation and detection operations, the rest is assumed to arise from error in the gate itself.…”

“…in the micrometer range. Solutions to this problem involve high static magnetic field gradient [10,11] or near-field microwave radiation [12]. Both schemes are promising for future scaling up of ion trap technology since here the control fields can be generated by electrodes that are integrated into the trap structure itself.…”

Anabiosis of phase distribution of a three-level atom

“…In the meantime, the quantum computing community has demonstrated the basic building blocks of a scalable ion trap quantum computer [8][9][10][11]. In this direction several schemes of coherent manipulation of the quantum states of trapped atoms have been developed [12].…”