Quantum bit encoding and information processing with field superposition states in a circuit

Neto, O. P. de Sá; Oliveira, M. C. de

doi:10.1088/0953-4075/45/18/185505

Cited by 10 publications

(12 citation statements)

References 32 publications

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“…(4.18) for α0 = 5. Other parameters as in Fig (7). Here, the optomechanical cat state decoheres for a storage time of 0.3466/Γm, which is the time a Wigner function loses its negativity according to Eq.…”

Section: B Interference Fringesmentioning

confidence: 99%

“…Schrödinger's cat [1] features in the investigation of a fundamental issue in quantum mechanics [2][3][4] namely: Does quantum mechanics hold true in the macroscopic world? This highly nonclassical state is also potentially useful, being proposed as a resource in many quantum information applications including quantum computation [5][6][7], quantum teleportation [8], quantum metrology [9,10] and cryptography [11]. As such, there has been much interest in creating Schrödinger cat states of increasing size [12][13][14][15][16][17][18][19][20][21][22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

“…(4.20) respectively. Other parameters as in Fig(7). This figure has a storage time of 0.02/Γm, too short for substantial decoherence.…”

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confidence: 99%

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Creation, storage, and retrieval of an optomechanical cat state

et al. 2018

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We analyze a method for the creation, storage and retrieval of optomechanical Schrödinger cat states, in which there is a quantum superposition of two distinct macroscopic states of a mechanical oscillator. In the quantum memory protocol, an optical cat state is first prepared in an optical cavity, then transferred to the mechanical mode, where it is stored and later retrieved using control fields. We carry out numerical simulations for the quantum memory protocol for optomechanical cat states using the positive-P phase space representation. This has a compact, positive representation for a cat state, thus allowing a probabilistic simulation of this highly non-classical quantum system. It is essential to use importance sampling to carry out the simulation effectively. To verify the effectiveness of the cat-state quantum memory, we consider several cat-state signatures and show how they can be computed. We also investigate the effects of decoherence on a cat state by solving the standard master equation for a simplified model analytically, allowing us to compare with the numerical results. Focusing on the negativity of the Wigner function as a signature of the cat state, we evaluate analytically an upper bound on the time taken for the negativity to vanish, for a given temperature of the environment of the mechanical oscillator. We show consistency with the numerical methods. These provide exact solutions, allowing a full treatment of decoherence in an experiment that involves creating, storing and retrieving mechanical cat states using temporally mode-matched input and output pulses. Our analysis treats the internal optical and mechanical modes of an optomechanical oscillator, and the complete set of input and output field modes which become entangled with the internal modes. The model includes decoherence due to thermal effects in the mechanical reservoirs, as well as optical and mechanical losses.

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Section: B Interference Fringesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Creation, storage, and retrieval of an optomechanical cat state

et al. 2018

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“…On the other hand, hybrid gates have attracted tremendous attention recently, because of their importance in connecting quantum information processors with different encoding information-processing units, as well as their significant application in transferring quantum states between a quantum processor and a quantum memory. A number of works on implementing hybrid gates with various qubits, qutrits or qudits have been presented (e.g., [33][34][35][36][37][38][39][40][41][42][43]). However, after a deep search of literature, we note that how to implement hybrid quantum gates with SC qutrits and cat-state qutrits (i.e., qutrits encoded via cat states) has not been studied yet.…”

Section: Introductionmentioning

confidence: 99%

Hybrid controlled-sum gate with one superconducting qutrit and one cat-state qutrit and application in hybrid entangled state preparation

Bin

Yang

2022

Phys. Rev. A

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Compared with a qubit, a qudit (i.e., d-level or d-state quantum system) provides a larger Hilbert space to store and process information. On the other hand, qudit-based hybrid quantum computing usually requires performing hybrid quantum gates with qudits different in their nature or in their encoding format. In this work, we consider the qutrit case, i.e., the case for a qudit with d=3. We propose a simple method to realize a hybrid quantum controlled-SUM gate with one superconducting (SC) qutrit and a cat-state qutrit. This gate plus single-qutrit gates form a universal set of ternary logic gates for quantum computing with qutrits. Our proposal is based on circuit QED and operates essentially by employing a SC ququart (a four-level quantum system) dispersively coupled to a microwave cavity. The gate implementation is quite simple because it only requires a single basic operation. Neither classical pulse nor measurement is needed. The auxiliary higher energy level of the SC ququart is virtually excited during the gate operation, thus decoherence from this level is greatly suppressed. As an application of this gate, we discuss the generation of a hybrid maximallyentangled state of one SC qutrit and one cat-state qutrit. We further analyze the experimental feasibility of creating such hybrid entangled state in circuit QED. This proposal is quite general and can be extended to accomplish the same task in a wide range of physical system, such as a four-level natural or artificial atom coupled to an optical or microwave cavity.

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“…Quantum gates, acting on hybrid qubits (i.e., different types of qubits), have attracted tremendous attention, because of their importance in connecting quantum information processors with different encoding qubits as well as their significant application in transferring quantum states between a quantum processor and a quantum memory. In recent years, many theoretical proposals have been presented for realizing a universal two-qubit controlled-phase (CP) or controlled-not (CNOT) gate with various hybrid qubits, such as a cat-state qubit and a charge qubit [1], a flying photonic qubit and an atomic qubit [2], a charge qubit and an atomic qubit [3], a spin qubit and a Majorana qubit [4], a photonic qubit and a superconducting qubit [5], and so on. Moreover, the two-qubit CP or CNOT gate with a flying optical photon and a single trapped atom [6], as well as the two-qubit CP gate with a 40 Ca + qubit and one 43 Ca + qubit [7] have been demonstrated in experiments.…”

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confidence: 99%

Universal quantum gate with hybrid qubits in circuit quantum electrodynamics

Yang

Zheng

2018

Opt. Lett.

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Hybrid qubits have recently drawn intensive attention in quantum computing. We here propose a method to implement a universal controlled-phase gate of two hybrid qubits via two threedimensional (3D) microwave cavities coupled to a superconducting flux qutrit. For the gate considered here, the control qubit is a microwave photonic qubit (particle-like qubit), whose two logic states are encoded by the vacuum state and the single-photon state of a cavity, while the target qubit is a cat-state qubit (wave-like qubit), whose two logic states are encoded by the two orthogonal cat states of the other cavity. During the gate operation, the qutrit remains in the ground state; therefore decoherence from the qutrit is greatly suppressed. The gate realization is quite simple, because only a single basic operation is employed and neither classical pulse nor measurement is used. Our numerical simulations demonstrate that with current circuit QED technology, this gate can be realized with a high fidelity. The generality of this proposal allows to implement the proposed gate in a wide range of physical systems, such as two 1D or 3D microwave or optical cavities coupled to a natural or artificial three-level atom. Finally, this proposal can be applied to create a novel entangled state between a particle-like photonic qubit and a wave-like cat-state qubit.

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Quantum bit encoding and information processing with field superposition states in a circuit

Cited by 10 publications

References 32 publications

Creation, storage, and retrieval of an optomechanical cat state

Creation, storage, and retrieval of an optomechanical cat state

Hybrid controlled-sum gate with one superconducting qutrit and one cat-state qutrit and application in hybrid entangled state preparation

Universal quantum gate with hybrid qubits in circuit quantum electrodynamics

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