Superconducting Circuits for Quantum Information: An Outlook

Devoret, Michel; Schoelkopf, Robert

doi:10.1126/science.1231930

Cited by 1,897 publications

(1,849 citation statements)

References 59 publications

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“…One natural example is the dipolar interaction between polar molecules, which is the focus of this Review. Of course, many other experimental platforms are also being pursued that feature long-range interactions, including highly magnetic atoms [7,8], trapped ions [9], superconducting circuits [10], Rydberg atoms [11], and atoms coupled to photonic structures [12].…”

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confidence: 99%

New frontiers for quantum gases of polar molecules

et al. 2016

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The field of ultracold quantum matter has burgeoned over the last few decades, thanks to the growing capabilities for atomic systems to be probed and manipulated with exquisite control. Researchers can now precisely create and study quantum manybody states that are effectively isolated from the external environment. Much of the work in ultracold matter has focused on systems of alkali or alkaline-earth atoms, mainly due to their ease of cooling. Extending this precise control to molecules has seen rapidly increasing interest and activity, as molecules possess additional degrees of freedom that make them useful for tests of fundamental physics, studying ultracold chemistry and collisions, and engineering qualitatively new types of quantum phases and quantum many-body systems. Here, we review one particularly fruitful research direction: the creation and manipulation of ultracold bialkali molecules. The recent success in creating a quantum gas of polar molecules opens many exciting research opportunities. Atomic, Molecular, and Optical (AMO) systems offer experimentalists the ability to precisely control interactions in a quantum many-body system [1,2], and a rich set of experiments has already been performed. Some prominent examples include studies of the BEC-BCS crossover in two-component Fermi gases [3,4,5] and the superfluid-Mott insulator transition in ultracold bosons loaded into a 3D optical lattice [6]. Neutral atomic systems normally have point-like contact interactions that can be parametrized with a single quantity, the scattering length a, which can be tuned via a Feshbach resonance [2]. In recent years, systems with long-range and anisotropic interactions have garnered much attention. One natural example is the dipolar interaction between polar molecules, which is the focus of this Review. Of course, many other experimental platforms are also being pursued that feature long-range interactions, including highly magnetic atoms [7,8], trapped ions The dipolar interaction exhibits several important attributes. First, the energy scales in dipolar systems are usually much larger than those in typical atomic alkali systems, making it easier to study interaction-driven structural properties and non-equilibrium dynamics. Second, and perhaps more importantly, the anisotropic and long-range nature of the interaction allows for the realization of novel quantum phases, especially when the spatial dimensions of the system can be varied with optical lattices. Some of these engineered systems may find relevance to outstanding problems in condensed-matter physics [13,14]; moreover, qualitatively new types of physics can emerge in the presence of long-range interactions [15,16,17,18,19,20,21]. As a specific example of a unique feature of long-range interactions, a spin-1/2 Hamiltonian can be encoded based on a pair of oppositeparity rotational states where dipolar interactions give rise to a direct spin exchange coupling between molecules [22,23]. With this scheme implemented in an optical lattice, many-body spin dynam...

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confidence: 99%

New frontiers for quantum gases of polar molecules

et al. 2016

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“…We refer to Hamiltonian (1) as an extended Rabi model due to the multiple excitation levels of the transmon. Despite this deviation from the Rabi model, quantitatively shown in Supplementary Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Superconducting circuits such as microwave cavities and Josephson junction based artificial atoms 1 have opened up a wealth of new experimental possibilities by enabling much stronger lightmatter coupling than in analog experiments with natural atoms 2 and by taking advantage of the versatility of engineered circuits. With strong coupling, 3 where the coupling is larger than the dissipation rates γ and κ of the atom and mode respectively, experiments such as photon-number resolution 4 or Schrödinger-cat revivals 5 have beautifully displayed the quantum physics of a single-atom coupled to the electromagnetic field of a single mode.…”

Section: Introductionmentioning

confidence: 99%

Multi-mode ultra-strong coupling in circuit quantum electrodynamics

et al. 2017

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With the introduction of superconducting circuits into the field of quantum optics, many experimental demonstrations of the quantum physics of an artificial atom coupled to a single-mode light field have been realized. Engineering such quantum systems offers the opportunity to explore extreme regimes of light-matter interaction that are inaccessible with natural systems. For instance the coupling strength g can be increased until it is comparable with the atomic or mode frequency ω a,m and the atom can be coupled to multiple modes which has always challenged our understanding of light-matter interaction. Here, we experimentally realize a transmon qubit in the ultra-strong coupling regime, reaching coupling ratios of g/ω m = 0.19 and we measure multi-mode interactions through a hybridization of the qubit up to the fifth mode of the resonator. This is enabled by a qubit with 88% of its capacitance formed by a vacuum-gap capacitance with the center conductor of a coplanar waveguide resonator. In addition to potential applications in quantum information technologies due to its small size, this architecture offers the potential to further explore the regime of multi-mode ultra-strong coupling. With strong coupling, 3 where the coupling is larger than the dissipation rates γ and κ of the atom and mode respectively, experiments such as photon-number resolution 4 or Schrödinger-cat revivals 5 have beautifully displayed the quantum physics of a single-atom coupled to the electromagnetic field of a single mode. As the field matures, circuits of larger complexity are explored, 6-8 opening the prospect of controllably studying systems that are theoretically and numerically difficult to understand.One example is the interaction between an (artificial) atom and an electromagnetic mode where the coupling rate becomes a considerable fraction of the atomic or mode eigen-frequency. This ultra-strong coupling (USC) regime, described by the quantum Rabi model, shows the breakdown of excitation number as conserved quantity, resulting in a significant theoretical challenge. 9,10 In the regime of g=ω a;m ' 1, known as deep-strong coupling (DSC), a symmetry breaking of the vacuum is predicted 11 (i.e., qualitative change of the ground state), similar to the Higgs mechanism or Jahn-Teller instability. To date, U/DSC with superconducting circuits has only been realized with flux qubits 6,12 or in the context of quantum simulations. 13,14 Using transmon qubits for USC is interesting due to their higher coherence rates 15 as well as their weakly-anharmonic nature, allowing the exploration of a different Hamiltonian than with flux qubits. 16 Since transmon qubits are currently a standard in quantum computing efforts, [17][18][19] implementing USC in a transmon architecture could also have technological applications by

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“…one Cooper-pair, as described by the third term on the right-hand-side of (1). How the corresponding displaced photon states couple depends on their overlap.…”

Section: Hamiltonian and Basis Statesmentioning

confidence: 99%

“…The combination of small Josephson junctions with superconducting microelectronics offer a versatile playground for quantum physics and quantum information, often called circuit-quantum electrodynamics or circuit-QED (1) . In particular, it is possible to engineer circuits that realize a number of fundamental quantum optical systems.…”

Section: Introductionmentioning

confidence: 99%

Effects of quasiparticle tunnelling in a circuit-QED realization of a strongly driven two-level system

Leppäkangas

Graaf

Adamyan

et al. 2013

J. Phys. B: At. Mol. Opt. Phys.

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Abstract. We experimentally and theoretically study the frequency shift of a driven cavity coupled to a superconducting charge qubit. In addition to previous studies, we here also consider drive strengths large enough to energetically allow for quasiparticle creation. Quasiparticle tunneling leads to the inclusion of more than two charge states in the dynamics. To explain the observed effects, we develop a master equation for the microwave dressed charge states, including quasiparticle tunneling. A bimodal behavior of the frequency shift as a function of gate voltage can be used for sensitive charge detection. However, at weak drives the charge sensitivity is significantly reduced by non-equilibrium quasiparticles, which induce transitions to a non-sensitive state. Unexpectedly, at high enough drives, quasiparticle tunneling enables a very fast relaxation channel to the sensitive state. In this regime, the charge sensitivity is thus robust against externally injected quasiparticles and the desired dynamics prevail over a broad range of temperatures. We find very good agreement between theory and experiment over a wide range of drive strengths and temperatures.

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Superconducting Circuits for Quantum Information: An Outlook

Cited by 1,897 publications

References 59 publications

New frontiers for quantum gases of polar molecules

New frontiers for quantum gases of polar molecules

Multi-mode ultra-strong coupling in circuit quantum electrodynamics

Effects of quasiparticle tunnelling in a circuit-QED realization of a strongly driven two-level system

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