Preparation and measurement of three-qubit entanglement in a superconducting circuit

By Leonardo DiCarlo, M. Reed, Luyan Sun, Blake R. Johnson, Jerry M. Chow, Jay M. Gambetta, Luigi Frunzio, Steven M. Girvin, Michel H. Devoret, Robert J. Schoelkopf. Nature, 2010

493 citations recorded by the source corpus.

Traditionally, quantum entanglement has been central to foundational discussions of quantum mechanics. The measurement of correlations between entangled particles can have results at odds with classical behaviour. These discrepancies grow exponentially with the number of entangled particles. With the ample experimental confirmation of quantum mechanical predictions, entanglement has evolved from a philosophical conundrum into a key resource for technologies such as quantum communication and computation. Although entanglement in superconducting circuits has been limited so far to two qubits, the extension of entanglement to three, eight and ten qubits has been achieved among spins, ions and photons, respectively. A key question for solid-state quantum information processing is whether an engineered system could display the multi-qubit entanglement necessary for quantum error correction, which starts with tripartite entanglement. Here, using a circuit quantum electrodynamics architecture, we demonstrate deterministic production of three-qubit Greenberger–Horne–Zeilinger (GHZ) states with fidelity of 88 per cent, measured with quantum state tomography. Several entanglement witnesses detect genuine three-qubit entanglement by violating biseparable bounds by 830 ± 80 per cent. We demonstrate the first step of basic quantum error correction, namely the encoding of a logical qubit into a manifold of GHZ-like states using a repetition code. The integration of this encoding with decoding and error-correcting steps in a feedback loop will be the next step for quantum computing with integrated circuits.

Subfields: Artificial Intelligence, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/2987bcb8bcc16bf7e5506ad6b2919f14c1dcf6ef

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Citations in the corpus

Implementation of a Toffoli gate with superconducting circuits (2011, methodology): “shown significant progress recently: two-qubit algorithms [10] and two-qubit process tomography have been implemented [11], three-qubit entangled states have been prepared [12, 13], first steps towards quantum teleportation have been taken [14] and work on quantum computing ar-”
Colloquium: Stimulating uncertainty: Amplifying the quantum vacuum with superconducting circuits (2011, background): “These advances have allowed for multiple qubit (DiCarlo et al., 2010; Majer et al., 2007; Sillianpää et al., 2007; Wei et al., 2006) and photon (Wang et al., 2011) entanglement using transmission lines that span distances of several millimeters, and are therefore visible to the naked eye.”
Circuit QED: Superconducting Qubits Coupled to Microwave Photons (2015, methodology): “…2010; Mariantoni et al., 2011a; Wang et al., 2011), entangle two (Ansmann et al., 2009; Chow et al., 2010) and three qubits (Neeley et al., 2010; DiCarlo et al., 2010), run simple quantum algorithms (DiCarlo et al., 2009; Mariantoni et al., 2011b) and perform rudimentary quantum error…”
Modular entanglement of atomic qubits using photons and phonons (2014, background): “son junctions through capacitive or inductive couplings [10, 11].”