Universal control of ion qubits in a scalable microfabricated planar trap

Abstract

We demonstrate universal quantum control over chains of ions in a surface-electrode ion trap, including all the fundamental operations necessary to perform algorithms in a one-dimensional, nearest-neighbor quantum computing architecture. We realize both single-qubit operations and nearest-neighbor entangling gates with Raman laser beams, and we interleave the two gate types. We report average single-qubit gate fidelities as high as 0.970(1) for two-, three-, and four-ion chains, characterized with randomized benchmarking. We generate Bell states between the nearest-neighbor pairs of a three-ion chain, with fidelity up to 0.84(2). We combine one-and two-qubit gates to perform quantum process tomography of a CNOTgate in a two-ion chain, and we report an overall fidelity of 0.76(3). System overviewThe experimental system is shown schematically in figure 1(a). We trap chains of 171 Yb + ions 60 μm above the surface-electrode ion trap described in [19]. This trap features through-chip vias instead of wirebonds. The

Measuring Anomalous Heating in a Planar Ion Trap with Variable Ion-Surface Separation

“…Therefore, anomalous heating is particularly prominent for microfabricated planar ion traps [14], where this separation can be as small as tens of micrometers. Microfabricated traps are central for the realization of scalable quantum information processing with trapped ions [14][15][16][17][18][19][20][21][22][23][24], and, therefore, in addition to its fundamental interest, it is of particular importance to characterize and understand anomalous heating.Though electric field noise-induced heating of ion motion has been studied in many experimental and theoretical works over the last years [1], one of the still open questions regarding anomalous heating is its dependence on the ion-electrode separation. In addition to being of practical use for ion trap design, knowing this dependence can confirm or contradict various existing theoretical models of anomalous heating.…”

Transport implementation of the Bernstein–Vazirani algorithm with ion qubits

“…We have implemented key upgrades to our system relative to the work in [20]. We now transmit one arm of our Raman beam pair through a 300 mm segment of photonic crystal fiber (LMA-PM-5, NKT Photonics) before it is focused down to the trapping region.…”

“…While we employ the same beam geometry as [20], system improvements have led to the increased gate fidelities reported in table 1. The principal improvement is to propagate one arm of our Raman beam pair through a segment of photonic crystal fiber [25].…”

“…To accommodate these phase shifts in the fewest number of physical p 2 rotations, we insert optimization gates O(j), where j is a free parameter in the gate compilation. As described in [20], the addition of these gates still produces the desired CNOT.…”

“…These populations have a drastic effect on algorithm fidelity and reduce the target output states below 80%. Preliminary work with the 'echo' decoupling technique discussed in [20] improves F Bell to 87.9(1.0)% and reduces P 1 to 3.4(4)%. The echo involves splitting the MS gate in half, ensuring the spin-motion entanglement is zero after each half, and inserting a Y gate on the targeted (or untargeted) ions after each half.…”