Generation of Nonclassical Microwave States Using an Artificial Atom in 1D Open Space

Hoi, I.-C.; Palomaki, Tauno; Lindkvist, Joel; Johansson, Göran; Delsing, Per; Wilson, Christopher

doi:10.1103/physrevlett.108.263601

Cited by 172 publications

(185 citation statements)

References 22 publications

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“…terms due to the much higher noise power of the HEMT amplifiers [28][29][30]. Figure 3 shows the three coherence functions g (2) α,β at zero delay τ as well as the noise reduction factor NRF, as a function of the photon pair emission rate Γ, the later being varied by scanning the flux threading the SQUID loop.…”

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confidence: 99%

Emission of Nonclassical Radiation by Inelastic Cooper Pair Tunneling

et al. 2017

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We show that a properly dc-biased Josephson junction in series with two microwave resonators of different frequencies emits photon pairs in the resonators. By measuring auto-and inter-correlations of the power leaking out of the resonators, we demonstrate two-mode amplitude squeezing below the classical limit. This non-classical microwave light emission is found to be in quantitative agreement with our theoretical predictions, up to an emission rate of 2 billion photon pairs per second. PACS numbers: 74.50+r, 73.23Hk, 85.25Cp Microwave radiation is usually produced by ac-driving a conductor like a wire antenna. The radiated field is then a so-called coherent state [1] which closely resembles a classical state. On the other hand, a simply dcbiased quantum conductor can also generate microwave radiation, owing to the probabilistic nature of the discrete charge transfer through the conductor which cause quantum fluctuations of the current [2][3][4]. In this latter situation, it is expected that the quantum character of the charge transfer may imprint in the properties of the emitted radiation, possibly leading to nonclassical radiation, such as e.g. antibunched photons [5][6][7][8][9][10][11]. More broadly, one may wonder what other types of interesting or useful nonclassical states of light can be generated with such a simple method. In this Letter, we investigate the properties of photons pairs emitted by a dc voltagebiased Josephson junction. In such a junction, at bias voltage less than the gap voltage 2∆/e, no quasiparticle excitation can be created in the superconducting electrodes. Thus, a DC current can only flow through the junction when the electrostatic energy 2eV associated to transfer of the charge of a Cooper pair through the circuit is absorbed by modes of the surrounding circuit [12][13][14][15][16][17].In order to obtain a situation in which the quantum nature of the emitted radiation can be probed quantitatively, we place such a dc-biased Josephson junction in an engineered environment made of two series resonators with different frequencies ν a , ν b , as shown in Fig. 1a. We consider in particular the resonance condition 2eV = h(ν a + ν b ), at which the transfer of a single Cooper pair is expected to create one photon in each resonator, leaking afterwards in two microwave lines. By measuring both photon emission rates as well as the power-power auto and intercorrelations, we prove that these correlations violate a Cauchy-Schwartz inequality obeyed by classical light, meaning that the relative fluctuations of the outgoing modes are suppressed below the classical limit. This two-mode amplitude squeezing is observed for emission rates as high as 2 × 10 9 photon pairs per second, making our setup a particularly bright (and simple) source of nonclassical radiation.Our experimental setup is shown in Fig. 1b 140 Ω. The resonators are connected to two separate bias tees making it possible to dc voltage bias the SQUID while collecting radiation on two separate microwave lines with wave impedance 50Ω....

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Emission of Nonclassical Radiation by Inelastic Cooper Pair Tunneling

et al. 2017

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“…In contrast to a system with discrete cavity modes, which is well described by the single mode or multimode Jaynes-Cummings Hamiltonian [16,17,18], a continuous density of states enables the formation of a localized state in the band gap. While other spin-boson problems with continuous DOS have also been studied experimentally [19,20] or theoretically [21,22] with superconducting circuits, this work explores physics near the band edge, where localized states emerge and reservoir engineering becomes possible.Light-matter interactions are being actively pursued using cold atoms coupled to optical photonic crystals [23,24], where the study of photonic band edge effects requires a combination of challenging nanostructure fabrication and optical laser trapping. Though impressive progress has been made, atoms are only weakly coupled to photonic crystal waveguides [24], potentially limiting the physics to the the perturbative regime.…”

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confidence: 99%

Quantum electrodynamics near a photonic bandgap

Liu¹,

Houck²

2016

Nature Phys

240

218

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Photonic crystals provide an extremely powerful toolset for manipulation of optical dispersion and density of states, and have thus been employed for applications from photon generation to quantum sensing with NVs and atoms [1, 2]. The unique control afforded by these media make them a beautiful, if unexplored, playground for strong coupling quantum electrodynamics, where a single, highly nonlinear emitter hybridizes with the bandstructure of the crystal. In this work we demonstrate that such hybridization can create localized cavity modes that live within the photonic bandgap, whose localization and spectral properties we explore in detail. We then demonstrate that the coloured vacuum of the photonic crystal can be employed for efficient dissipative state preparation. This work opens exciting prospects for engineering long-range spin models [3, 4] in the circuit QED architecture, as well as new opportunities for dissipative quantum state engineering.The perturbative effect of a structured vacuum is the renowned Purcell effect which states that the lifetime of an atom in such space will be proportional to the local photonic density of states (DOS) near the atomic transition frequency. In practice, the birth of the photonic crystal, which greatly modifies the vaccuum fluctuations, has enabled the control of spontaneous emission of various emitters such as quantum dots [5,6], magnons [7] and superconducting qubits [8]. However, when an atom is strongly coupled to a photonic crystal, non-perturbative effects become important and significantly enrich the physics. For instance, a single photon bound state has been predicted to emerge within the gap [9], and spontaneous emission of the atom will thus exhibit Rabi oscillation and light trapping behavior. In contrast to electronic band-gap systems, even multiple photons can be simultaneously localized by a single atom, and the coherent photonic transport within the otherwise forbidden band-gap can have a strongly correlated nature [10, 2,12]. In contrast to a system with discrete cavity modes, which is well described by the single mode or multimode Jaynes-Cummings Hamiltonian [16,17,18], a continuous density of states enables the formation of a localized state in the band gap. While other spin-boson problems with continuous DOS have also been studied experimentally [19,20] or theoretically [21,22] with superconducting circuits, this work explores physics near the band edge, where localized states emerge and reservoir engineering becomes possible.Light-matter interactions are being actively pursued using cold atoms coupled to optical photonic crystals [23,24], where the study of photonic band edge effects requires a combination of challenging nanostructure fabrication and optical laser trapping. Though impressive progress has been made, atoms are only weakly coupled to photonic crystal waveguides [24], potentially limiting the physics to the the perturbative regime. In this letter, using a microwave photonic crystal and a superconducting transmon qubit, we are able to r...

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“…The lack of any correlations prove that A and B correspond to two independent QDs. The data are taken at 0 T. forms than considered here, for instance to the case of atoms in photonic-crystal structures [27,28], nitrogen vacancy center in diamonds, or superconducting qubits [29]. In the context of photon transport and scattering, chiral waveguide may be used to create novel topological states of photons that even could be exploited in a new regime of strong nonlinear photon interactions.…”

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Deterministic photon–emitter coupling in chiral photonic circuits

et al. 2015

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The ability to engineer photon emission and photon scattering is at the heart of modern photonics applications ranging from light harvesting, through novel compact light sources, to quantuminformation processing based on single photons. Nanophotonic waveguides are particularly well suited for such applications since they confine photon propagation to a 1D geometry thereby increasing the interaction between light and matter. Adding chiral functionalities to nanophotonic waveguides lead to new opportunities enabling integrated and robust quantum-photonic devices or the observation of novel topological photonic states. In a regular waveguide, a quantum emitter radiates photons in either of two directions, and photon emission and absorption are reverse processes. This symmetry is violated in nanophotonic structures where a non-transversal local electric field implies that both photon emission [1,2] and scattering [3] may become directional. Here we experimentally demonstrate that the internal state of a quantum emitter determines the chirality of single-photon emission in a specially engineered photonic-crystal waveguide. Single-photon emission into the waveguide with a directionality of more than 90% is observed under conditions where practically all emitted photons are coupled to the waveguide. Such deterministic and highly directional photon emission enables on-chip optical diodes, circulators operating at the single-photon level, and deterministic quantum gates. Based on our experimental demonstration, we propose an experimentally achievable and fully scalable deterministic photon-photon CNOT gate, which so far has been missing in photonic quantum-information processing where most gates are probabilistic [4]. Chiral photonic circuits will enable dissipative preparation of entangled states of multiple emitters [5], may lead to novel topological photon states [6,7], or can be applied in a classical regime to obtain highly directional photon scattering [8][9][10].Truly 1D photon-emitter interfaces are desirable for a range of applications in photonic quantum-information processing [11]. To this end, photonic-crystal waveguides constitute an ideal platform featuring on-chip integration with the ability to engineer the light-matter coupling. Recent experiments have achieved a coupling efficiency for a single quantum dot (QD) to a photoniccrystal waveguide in excess of 98%, thus constituting a deterministic 1D photon-emitter interface [12]. Standard photonic-crystal waveguides are mirror symmetric around the center of the waveguide and as a consequence the mode polarization is predominantly linear at the positions where light intensity is high. By designing a photonic-crystal waveguide that breaks this symmetry, modes that are circularly polarized at the field maxima can be engineered. We refer to this novel type of waveguide as a glide-plane waveguide (GPW), cf. Supplementary Material for further descriptions of the structural parameters. In a GPW, a QD with a circularly polarized transition dipole emits preferential...

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Generation of Nonclassical Microwave States Using an Artificial Atom in 1D Open Space

Cited by 172 publications

References 22 publications

Emission of Nonclassical Radiation by Inelastic Cooper Pair Tunneling

Emission of Nonclassical Radiation by Inelastic Cooper Pair Tunneling

Quantum electrodynamics near a photonic bandgap

Deterministic photon–emitter coupling in chiral photonic circuits

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