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Register a new userMixing of coherent waves on a single three-level artificial atom
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Added by
Teresa H\\\"onigl-Decrinis
Publication date
2018
fields
Physics
and research's language is
English
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We report coherent frequency conversion in the gigahertz range via three-wave mixing on a single artificial atom in open space. All frequencies involved are in vicinity of transition frequencies of the three-level atom. A cyclic configuration of levels is therefore essential, which we have realised with an artificial atom based on the flux qubit geometry. The atom is continuously driven at two transition frequencies and we directly measure the coherent emission at the sum or difference frequency. Our approach enables coherent conversion of the incoming fields into the coherent emission at a designed frequency in prospective devices of quantum electronics.
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A number of superconducting qubits, such as the transmon or the phase qubit, have an energy level structure with small anharmonicity. This allows for convenient access of higher excited states with similar frequencies. However, special care has to be taken to avoid unwanted higher-level populations when using short control pulses. Here we demonstrate the preparation of arbitrary three-level superposition states using optimal control techniques in a transmon. Performing dispersive read-out we extract the populations of all three levels of the qutrit and study the coherence of its excited states. Finally we demonstrate full quantum state tomography of the prepared qutrit states and evaluate the fidelities of a set of states, finding on average 96%.
A single superconducting artificial atom provides a unique basis for coupling electromagnetic fields and photons hardly achieved with a natural atom. Bringing a pair of harmonic oscillators into resonance with transitions of the three-level atom converts atomic spontaneous processes into correlated emission dynamics. We demonstrate two-mode correlated emission lasing on harmonic oscillators coupled via the fully controllable three-level artificial atom. Correlation of two different color emissions reveals itself as equally narrowed linewiths and quench of their mutual phase-diffusion. The mutual linewidth is more than four orders of magnitude narrower than the Schawlow-Townes limit. The interference between the different color lasing fields demonstrates the two-mode fields are strongly correlated.
We present experimental observation of electromagnetically induced transparency (EIT) on a single macroscopic artificial atom (superconducting quantum system) coupled to open 1D space of a transmission line. Unlike in a optical media with many atoms, the single atom EIT in 1D space is revealed in suppression of reflection of electromagnetic waves, rather than absorption. The observed almost 100 % modulation of the reflection and transmission of propagating microwaves demonstrates full controllability of individual artificial atoms and a possibility to manipulate the atomic states. The system can be used as a switchable mirror of microwaves and opens a good perspective for its applications in photonic quantum information processing and other fields.
Three-wave mixing in second-order nonlinear optical processes cannot occur in atomic systems due to the electric-dipole selection rules. In contrast, we demonstrate that second-order nonlinear processes can occur in a superconducting quantum circuit (i.e., a superconducting artificial atom) when the inversion symmetry of the potential energy is broken by simply changing the applied magnetic flux. In particular, we show that difference- and sum-frequencies (and second harmonics) can be generated in the microwave regime in a controllable manner by using a single three-level superconducting flux quantum circuit (SFQC). For our proposed parameters, the frequency tunability of this circuit can be achieved in the range of about 17 GHz for the sum-frequency generation, and around 42 GHz (or 26 GHz) for the difference-frequency generation. Our proposal provides a simple method to generate second-order nonlinear processes within current experimental parameters of SFQCs.
Quantum effects, prevalent in the microscopic scale, generally elusive in macroscopic systems due to dissipation and decoherence. Quantum phenomena in large systems emerge only when particles are strongly correlated as in superconductors and superfluids. Cooperative interaction of correlated atoms with electromagnetic fields leads to superradiance, the enhanced quantum radiation phenomenon, exhibiting novel physics such as quantum Dicke phase and ultranarrow linewidth for optical clocks. Recent researches to imprint atomic correlation directly demonstrated controllable collective atom-field interactions. Here, we report cavity-mediated coherent single-atom superradiance. Single atoms with predefined correlation traverse a high-Q cavity one by one, emitting photons cooperatively with the atoms already gone through the cavity. Such collective behavior of time-separated atoms is mediated by the long-lived cavity field. As a result, a coherent field is generated in the steady state, whose intensity varies as the square of the number of traversing atoms during the cavity decay time, exhibiting more than ten-fold enhancement from noncollective cases. The correlation among single atoms is prepared with the aligned atomic phase achieved by nanometer-precision position control of atoms with a nanohole-array aperture. The present work deepens our understanding of the collective matter-light interaction and provides an advanced platform for phase-controlled atom-field interactions.
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