Synthesizing three-body interaction of spin chirality with superconducting qubits

Abstract

Superconducting qubits provide a competitive platform for quantum simulation of complex dynamics that lies at the heart of quantum many-body systems, because of the flexibility and scalability afforded by the nature of microfabrication. However, in a multiqubit device, the physical form of couplings between qubits is either an electric (capacitor) or magnetic field (inductor), and the associated quadratic field energy determines that only two-body interaction in the Hamiltonian can be directly realized. Here we propose and experimentally synthesize the three-body spin-chirality interaction in a superconducting circuit based on Floquet engineering. By periodically modulating the resonant frequencies of the qubits connected with each other via capacitors, we can dynamically turn on and off qubit-qubit couplings, and further create chiral flows of the excitations in the three-qubit circular loop. Our result is a step toward engineering dynamical and many-body interactions in multiqubit superconducting devices, which potentially expands the degree of freedom in quantum simulation tasks.

Chiral current in Floquet cavity-magnonics

“…Chirality [24,25] plays an important role in the fractional quantum Hall effect in the magnetic materials, that could be simulated by optical lattice [26]. Spin chirality arises from the three-body interactions, which has been experimentally realized in the platform of superconducting qubits [27]. The chirality operator of three spins is Ô = σ 1 • ( σ 2 × σ 3 ), where σ j ≡ (σ x j , σ y j , σ z j ) is the Pauli vector for the jth spin particle.…”

“…The chirality operator of three spins is Ô = σ 1 • ( σ 2 × σ 3 ), where σ j ≡ (σ x j , σ y j , σ z j ) is the Pauli vector for the jth spin particle. It is straightforward to verify that Ô breaks both the time reversal symmetry T (replacing σ j by − σ j ) and the parity symmetry P (exchanging σ j with σ k ) but conserves the PT symmetry [27]. The dynamics of the spins driven by Ô features a chiral evolution, i.e., |s 1 s 2 s 3 → |s 2 s 3 s 1 → |s 3 s 1 s 2 , where s j = 0 (spin down) or 1 (spin up) [28].…”

“…Floquet engineering by fast periodic modulation over the characteristic frequencies of a quantum system is a major control approach to the long-time dynamics of the system [31,[34][35][36], where the effective Hamiltonian can be synthesized through designing appropriate drives. Floquet engineering has been used to realize quantum switch [37], chiral ground state current [38], quantum simulation [39], and perfect state transfer [27,40,41] in superconducting qubits.…”

Synthesizing five-body interaction in a superconducting quantum circuit

“…The anti-symmetric spinexchange interaction (Dzyaloshinskii-Moriya interaction) [9,10] has been synthesized by breaking the time-reversal symmetry through Floquet modulation [11], enabling a three-qubit chiral quantum gate for entangling qubits more efficiently than the two-qubit gates [12]. Similar techniques have been applied to the synthesis of effective gauge field [13] and three-spin chirality Hamiltonian [14], which is a necessary element in simulating chiral spin liquid [15] and promising to realize the topological states of quantized light [16][17][18]. Four-spin ring-exchange interaction, which has been synthesized in optical lattices of cold atoms [19], is essential for toric codes in topological quantum computing [20].…”

Distinguishing multi-spin interactions from lower-order effects

“…While many n-local coupling proposals use perturbative Hamiltonian gadgets with ancilla qubits to obtain the effective interaction [11][12][13][14], a variety of nongadgetized 3-and 4-local interaction schemes have been proposed [15][16][17][18][19][20], some of which are scalable to higherorder locality. While the implementation of such interactions appears to be of broad interest, the identification of multi-spin interactions when these are relatively weak and appear in combination with interactions of other orders that are of comparable strength or larger remains an open question.…”