Vacuum-induced Autler-Townes splitting in a superconducting artificial atom

Abstract

We experimentally study a vacuum-induced Autler-Townes doublet in a superconducting threelevel artificial atom strongly coupled to a coplanar waveguide resonator and simultaneously to a transmission line. The Autler-Townes splitting is observed in the reflection spectrum from the three-level atom in a transition between the ground state and the second excited state when the transition between the two excited states is resonant with a resonator. By applying a driving field to the resonator, we observe a change in the regime of the Autler-Townes splitting from quantum (vacuum-induced) to classical (with many resonator photons). Furthermore, we show that the reflection of propagating microwaves in a transmission line could be controlled by different frequency single photons in a resonator. PACS numbers: 42.50.Lc, 42.65.Lm, 85.25.Cp Electromagnetic waves propagating through a medium of identical atoms are resonantly absorbed. The absorption can be eliminated when a strong driving field couples other atomic transitions in, for example, three-level atoms, creating a transparency window for the waves. This results in either Autler-Townes splitting (ATS) [1] or electromagnetically induced transparency (EIT) [2,3] and is extensively studied in quantum optics [4,5]. The same phenomena can be observed even if the medium is replaced by a single atom or a molecule which is coupled to either a cavity [6,7] or an open space [8,9]. However, the strong coupling between the driving field and a single natural atom is difficult to achieve. Recently, the strong coupling has been experimentally achieved between a superconducting artificial atom and non-quantized microwave fields confined in a one-dimensional transmission line [10]. This enables ATS and EIT to be observed using a single superconducting artificial atom [11][12][13][14]. Several experiments have already shown ATS [15][16][17][18][19][20][21][22] and state manipulation [23,24] in a single three-level artificial atom. ATS [25] and EIT [26] have been demonstrated in a Jaynes-Cummings ladder system of a single two-level artificial atom dispersively coupled to a cavity.The observation of both ATS and EIT in a medium (an ensemble of atoms) usually requires strong classical driving fields. However, the conditions are different: the driving field required for the observation of EIT is weaker than that for ATS, and there is a crossover from ATS to EIT [27,28]. In particular, in ATS the splitting is determined by the Rabi frequency of the driving field, whereas in EIT the dip between the two peaks is a result of quantum interference. These effects take place even if the medium is scaled down to a single atom and the driving field is quantized. The condition for the observation of the effects can then be reduced to a small number of photons or even without photons owing to coupling to a vacuum mode. Theoretical investigations show that the transparency for the classical probing field can still occur [29]. This has potentially important applications, for example, in single-photon...

A phononic crystal coupled to a transmission line via an artificial atom

“…It is a direct consequence of the differences of the modes field distribution functions A ij (x), which affect the value of integral in Eqs. (4), (5). In particular, for the mode f 0,1 the coupling is large, while for an adjacent odd mode f 1,1 it is zero.…”

“…Such systems are also very interesting for fundamental physics, especially for quantum optics with artificial atoms [1][2][3][4] and for implementing them in new research directions. One of the most important properties of such systems is that they can easily achieve the strong coupling regime even to several macroscopic circuit elements 5 . Recently, several groups have demonstrated Quantum Acoustodynamics (QAD) with the artificial atoms, where electromagnetic waves are replaced by acoustic ones and photons by phonons [6][7][8] .…”

Dynamic Stark shift in a Doppler-broadened four-wave mixing

“…As the splitting amplitude depends on the Rabi frequency of the transitions, the AT splitting has been used to measure transition dipole moments and lifetimes of highly excited states [5,6]. Other applications include quantum memory storage [7] and microwave propagation in transmission lines [8], for instance.…”

Witnessing entanglement via the geometric phase in a impurity-doped Bose-Einstein condensate

“…In particular, it is one of fascinating problems in the field of quantum physics and quantum information to detect quantum entanglement of a micro-macro system [8][9][10][11][12][13][14][15][16][17][18][19][20][21]. The difficulties inherent in such a question are manifolds, and they are related not only to quantum decoherence induced by the surrounding environment [22][23][24][25][26][27][28][29][30][31][32], but also to a measurement precision sufficient to observe quantum effects at such macroscales.…”