Superconducting qubit-resonator-atom hybrid system (original) (raw)
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Quantum State Transmission in a Superconducting Charge Qubit-Atom Hybrid
Scientific reports, 2016
Hybrids consisting of macroscopic superconducting circuits and microscopic components, such as atoms and spins, have the potential of transmitting an arbitrary state between different quantum species, leading to the prospective of high-speed operation and long-time storage of quantum information. Here we propose a novel hybrid structure, where a neutral-atom qubit directly interfaces with a superconducting charge qubit, to implement the qubit-state transmission. The highly-excited Rydberg atom located inside the gate capacitor strongly affects the behavior of Cooper pairs in the box while the atom in the ground state hardly interferes with the superconducting device. In addition, the DC Stark shift of the atomic states significantly depends on the charge-qubit states. By means of the standard spectroscopic techniques and sweeping the gate voltage bias, we show how to transfer an arbitrary quantum state from the superconducting device to the atom and vice versa.
Long coherence times for Rydberg qubits on a superconducting atom chip
Physical Review A, 2014
Superconducting atom chips and Rydberg atoms are promising tools for quantum information processing operations based on the dipole blockade effect. Nevertheless, one has to face the severe problem of stray electric fields in the vicinity of the chip. We demonstrate a simple method circumventing this problem. Microwave spectroscopy reveals extremely long coherence lifetimes (in the millisecond range) for a qubit stored in a Rydberg level superposition close to the chip surface. This is an essential step for the development of quantum simulation with Rydberg atoms and of a hybrid quantum information architecture based on atomic ensembles and superconducting circuits.
Reversible state transfer between superconducting qubits and atomic ensembles
Physical Review A, 2009
We examine the possibility of coherent, reversible information transfer between solid-state superconducting qubits and ensembles of ultra-cold atoms. Strong coupling between these systems is mediated by a microwave transmission line resonator that interacts near-resonantly with the atoms via their optically excited Rydberg states. The solid-state qubits can then be used to implement rapid quantum logic gates, while collective metastable states of the atoms can be employed for long-term storage and optical read-out of quantum information.
Implementation of a Toffoli gate with superconducting circuits
Nature, 2011
The quantum Toffoli gate allows universal reversible classical computation. It is also an important primitive in many quantum circuits and quantum error correction schemes. Here we demonstrate the realization of a Toffoli gate with three superconducting transmon qubits coupled to a microwave resonator. By exploiting the third energy level of the transmon qubit, the number of elementary gates needed for the implementation of the Toffoli gate, as well as the total gate time can be reduced significantly in comparison to theoretical proposals using two-level systems only. We characterize the performance of the gate by full process tomography and Monte Carlo process certification. The gate fidelity is found to be 64.5 ± 0.5%.
Physical Review A, 2005
We describe the design for a scalable, solid-state quantum-information-processing architecture based on the integration of GHz-frequency nanomechanical resonators with Josephson tunnel junctions, which has the potential for demonstrating a variety of single-and multiqubit operations critical to quantum computation. The computational qubits are eigenstates of large-area, current-biased Josephson junctions, manipulated and measured using strobed external circuitry. Two or more of these phase qubits are capacitively coupled to a high-quality-factor piezoelectric nanoelectromechanical disk resonator, which forms the backbone of our architecture, and which enables coherent coupling of the qubits. The integrated system is analogous to one or more few-level atoms ͑the Josephson junction qubits͒ in an electromagnetic cavity ͑the nanomechanical reso-nator͒. However, unlike existing approaches using atoms in electromagnetic cavities, here we can individually tune the level spacing of the "atoms" and control their "electromagnetic" interaction strength. We show theoretically that quantum states prepared in a Josephson junction can be passed to the nanomechanical resonator and stored there, and then can be passed back to the original junction or transferred to another with high fidelity. The resonator can also be used to produce maximally entangled Bell states between a pair of Josephson junctions. Many such junction-resonator complexes can be assembled in a hub-and-spoke layout, resulting in a large-scale quantum circuit. Our proposed architecture combines desirable features of both solid-state and cavity quantum electrodynamics approaches, and could make quantum-information processing possible in a scalable, solid-state environment.
Optimized driving of superconducting artificial atoms for improved single-qubit gates
Physical Review A, 2010
We employ pulse shaping to abate single-qubit gate errors arising from the weak anharmonicity of transmon superconducting qubits. By applying shaped pulses to both quadratures of rotation, a phase error induced by the presence of higher levels is corrected. Using a derivative of the control on the quadrature channel, we are able to remove the effect of the anharmonic levels for multiple qubits coupled to a microwave resonator. Randomized benchmarking is used to quantify the average error per gate, achieving a minimum of 0.007 ± 0.005 using 4 ns-wide pulse.
Quantum state synthesis of superconducting resonators
Physical Review A, 2016
We present a theoretical analysis of different methods to synthesize entangled states of two quantum mechanical resonators. These methods are inspired by experimentally demonstrated interactions of superconducting resonators with artificial atoms, and offer efficient routes to generate nonclassical states. Using a two-mode Jaynes-Cummings model, we analyze the theoretical structure of these algorithms and their average performance for arbitrary states and for deterministically preparing NOON and maximally entangled states. Using a new state synthesis algorithm, we show that NOON and maximally entangled states can be prepared in a time linear in the desired photon number and without any state-selective interactions.
Tunable Coupling of Superconducting Qubits
Physical Review Letters, 2003
We study an LC-circuit implemented using a current-biased Josephson junction (CBJJ) as a tunable coupler for superconducting qubits. By modulating the bias current, the junction can be tuned in and out of resonance and entangled with the qubits coupled to it. One can thus implement two-qubit operations by mediating entanglement. We consider the examples of CBJJ and chargephase qubits. A simple recoupling scheme leads to a generalization to arbitrary qubit designs.
Hybrid Quantum Circuit with a Superconducting Qubit Coupled to a Spin Ensemble
Physical Review Letters, 2011
Present-day implementations of quantum information processing rely on two widely different types of quantum bits (qubits). On the one hand, microscopic systems such as atoms or spins are naturally well decoupled from their environment and as such can reach extremely long coherence times ; on the other hand, more macroscopic objects such as superconducting circuits are strongly coupled to electromagnetic fields, making them easy to entangle although with shorter coherence times . It thus seems appealing to combine the two types of systems in hybrid structures that could possibly take the best of both worlds. Here we report the first experimental realization of a hybrid quantum circuit in which a superconducting qubit of the transmon type is coherently coupled to a spin ensemble consisting of nitrogen-vacancy (NV) centers in a diamond crystal [8] via a frequency-tunable superconducting resonator acting as a quantum bus. Using this circuit, we prepare arbitrary superpositions of the qubit states that we store into collective excitations of the spin ensemble and retrieve back later on into the qubit. We demonstrate that this process preserves quantum coherence by performing quantum state tomography of the qubit. These results constitute a first proof of concept of spin-ensemble based quantum memory for superconducting qubits [12]. As a landmark of the successful marriage between a superconducting qubit and electronic spins, we detect with the qubit the hyperfine structure of the NV center.
01 9 v 2 9 O ct 2 00 6 Realization of a superconducting atom chip
We have trapped rubidium atoms in the magnetic field produced by a superconducting atom chip operated at liquid Helium temperatures. Up to 8.2 • 10 5 atoms are held in a Ioffe-Pritchard trap at a distance of 440 µm from the chip surface, with a temperature of 40 µK. The trap lifetime reaches 115 s at low atomic densities. These results open the way to the exploration of atom-surface interactions and coherent atomic transport in a superconducting environment, whose properties are radically different from normal metals at room temperature.