Universal logic gates for two quantum bits (qubits) form an essential ingredient of quantum computation. Dynamical gates have been proposed in the context of trapped ions; however, geometric phase gates (which change only the phase of the physical qubits) offer potential practical advantages because they have higher intrinsic resistance to certain small errors and might enable faster gate implementation. Here we demonstrate a universal geometric pi-phase gate between two beryllium ion-qubits, based on coherent displacements induced by an optical dipole force. The displacements depend on the internal atomic states; the motional state of the ions is unimportant provided that they remain in the regime in which the force can be considered constant over the extent of each ion's wave packet. By combining the gate with single-qubit rotations, we have prepared ions in an entangled Bell state with 97% fidelity-about six times better than in a previous experiment demonstrating a universal gate between two ion-qubits. The particular properties of the gate make it attractive for a multiplexed trap architecture that would enable scaling to large numbers of ion-qubits.

The generation of entanglement is a fundamental resource for quantum technology, and trapped ions are one of the most promising systems for storage and manipulation of quantum information. Here we study the speed/fidelity trade-off for a two-qubit phase gate implemented in 43 Ca + hyperfine trapped-ion qubits. We characterize various error sources contributing to the measured fidelity, allowing us to account for errors due to single-qubit state preparation, rotation and measurement (each at the ∼ 0.1% level), and to identify the leading sources of error in the two-qubit entangling operation. We achieve gate fidelities ranging between 97.1(2)% (for a gate time t g = 3.8µs) and 99.9(1)% (for t g = 100µs), representing respectively the fastest and lowest-error two-qubit gates reported between trapped-ion qubits by nearly an order of magnitude in each case.We perform a two-qubit geometric phase gate in the σ z basis [1], where the qubits are stored in the S states of the ground hyperfine manifold of 43 Ca + . The two-qubit gate operation is implemented by a pair of Raman laser beams at a detuning ∆ from the 4S 1/2 ↔ 4P 1/2 transition. To vary t g we adjust ∆ while holding the Raman beam intensity constant (at 5 mW per beam in a spot size of w = 27 µm); smaller ∆ enables a faster gate, at the cost of increased error due to photon scattering [2]. The Raman difference frequency is δ = ν z + δ g where δ g = 2/t g and the axial trap frequency is ν z = 1.95 MHz. The Raman beams propagate at 45• to the trap z-axis, such that their wave-vector difference is along z. We cool both axial modes of the ions close to the ground state of motion by Raman sideband cooling; the centre-of-mass mode, rather than the stretch mode, is used to implement the gate to avoid coupling to the (uncooled) radial modes of the trap [3].We embed the phase gate within a single-qubit spin-echo sequence [4], which ideally produces the Bell state |ψ + = (|↓↓ + |↑↑ )/ √ 2, and then use a further single-qubit rotation to measure the fidelity F = ψ + |ρ|ψ + of the state ρ obtained [1]. Thus the measured Bell state infidelity includes both errors due to the gate operation itself and errors in the single-qubit operations. We calibrate all single-qubit errors by independent experiments in order to extract the two-qubit gate error. The errors in the single-qubit operations are comparable to or smaller than the gate error over the parameter regime studied.Results are shown in figure 1, where we have normalized for qubit readout errors (17×10 −4 ). The data are in reasonable agreement with our error model for t g < ∼ 200 µs; we attribute the excess error for longer t g to the effect of single-qubit dephasing errors (arising from the influence of magnetic field noise on the field-sensitive qubit states). The lowest gate error is found at t g = 100 µs (using ∆ = −3.0 THz), where the measured Bell state fidelity is F = 0.9975(7). For this run, the single-qubit error contribution is modelled to be 14×10 −4 , and we infer a gate error of g = 11(7) × 10 −4 . This is ...

We implement all single-qubit operations with fidelities significantly above the minimum threshold required for fault-tolerant quantum computing, using a trapped-ion qubit stored in hyperfine "atomic clock" states of ^{43}Ca^{+}. We measure a combined qubit state preparation and single-shot readout fidelity of 99.93%, a memory coherence time of T_{2}^{*}=50  sec, and an average single-qubit gate fidelity of 99.9999%. These results are achieved in a room-temperature microfabricated surface trap, without the use of magnetic field shielding or dynamic decoupling techniques to overcome technical noise.

The nuclear export protein XPO1 is overexpressed in cancer, leading to the cytoplasmic mislocalization of multiple tumor suppressor proteins. Existing XPO1-targeting agents lack selectivity and have been associated with significant toxicity. Small molecule selective inhibitors of nuclear export (SINEs) were designed that specifically inhibit XPO1. Genetic experiments and X-ray structures demonstrate that SINE covalently bind to a cysteine residue in the cargo-binding groove of