Simple preparation of Bell and Greenberger-Horne-Zeilinger states using ultrastrong-coupling circuit QED

Abstract

The ability to entangle quantum systems is crucial for many applications in quantum technology, including quantum communication and quantum computing. Here, we propose a new, simple, and versatile setup for deterministically creating Bell and Greenberger-Horne-Zeilinger (GHZ) states between photons of different frequencies in a two-step protocol. The setup consists of a quantum bit (qubit) coupled ultrastrongly to three photonic resonator modes. The only operations needed in our protocol are to put the qubit in a superposition state, and then tune its frequency in and out of resonance with sums of the resonator-mode frequencies. By choosing which frequency we tune the qubit to, we select which entangled state we create. We show that our protocol can be implemented with high fidelity using feasible experimental parameters in state-of-the-art circuit quantum electrodynamics. One possible application of our setup is as a node distributing entanglement in a quantum network.

All‐Resonance Controlled‐Phase Gate on Two Nonlocal Nitrogen‐Vacancy Center Ensembles Assisted by a Superconducting Quantum Circuit

“…Universal quantum logical gates [ 1–3 ] are basic elements of universal quantum computing. Recently, the realization of gates has attracted much attention in many quantum systems, such as atoms, [ 4,5 ] cavity quantum electrodynamics (QED), [ 6–9 ] nuclear magnetic resonances, [ 10,11 ] quantum dots, [ 12,13 ] photons, [ 14–18 ] circuit QED, [ 19–21 ] and diamond nitrogen‐vacancy (NV) centers. [ 22,23 ] Each quantum system has its advantages and disadvantages.…”

Simulating ultrastrong-coupling processes breaking parity conservation in Jaynes-Cummings systems

“…Compared to strong coupling (SC; η < 0.1, but g larger than the loss rates in the system), USC opens new perspectives for efficiently simulating known effects and observing fundamentally new phenomena in quantum nonlinear optics [7][8][9][10][11][12][13][14][15][16][17], quantum field theory, supersymmetric (SUSY) field theories [18], cavity optomechanics [19][20][21][22][23][24][25][26], quantum plasmonics [21,[27][28][29], light-induced superconductivity [30,31], quantum thermodynamics [32], photochemistry (chemistry QED) [33][34][35][36], as well as metamaterial and material sciences. Ultrastrong coupling also has applications in quantum metrology and spectroscopy [37], and quantum information processing [13,[38][39][40][41][42][43].…”

Generating NOON states in circuit QED using a multiphoton resonance in the presence of counter-rotating interactions

“…With respect to the ratio of coupling strength and the characteristic frequency in the Rabi model, g/ω ≃ 0.1 is a rough starting point of the strongcoupling regime [31]. In the strongly coupled qubit-cavity systems, Rabi Hamiltonians [33,34] have been applied in the protocol [11] to prepare the Bell states and the GHZ states. Without the counter-rotating terms, it is impossible to achieve a desired effective Hamiltonian connecting states with no conservation of the number of photons or excitons from the full Hamiltonian.…”