Quantum Optics Seminar by Pavel Bushev – Niels Bohr Institute - University of Copenhagen

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Quantum Optics Seminar by Pavel Bushev

//Cancelled// The present quantum technology relies on two main types of systems. The first one is based on using of single atoms, ions or spins, which often possess a long coherence time due to their intrinsic decoupling from the environment. The second type employs macroscopic objects such as superconducting (SC) quantum circuits that are strongly coupled to a microwave field [1]. However, despite of the nanosecond timescale in processing of quantum information, most of the SC-qubits are hindered by decoherence and therefore, their operation time is bounded by a few microseconds. Thus, connecting atomic and macroscopic approaches within a hybrid quantum architecture could possibly combine their best features.

I will outline the first experiments on spectroscopy of an erbium ion spin ensemble strongly coupled to a microwave superconducting resonator. Erbium ions are distinct from other spin ensembles [2,3] due to their optical transitions inside the telecom C-band at 1.54 μm. This feature makes them most attractive for the interfacing of optical and microwave photons [4]. The large spin tuning rate of ~200 GHz/T makes erbium also favorable for its integration with SC circuits. However, contrary to NV-centers or Cr3+ ions in ruby, rare-earth ions possess a magnetic anisotropy. That results in a strong angular dependence of the spin g-factor and the collective coupling strength on the orientation of the magnetic field. We have studied such angular variations of the coupling strength of an Er3+:Y2SiO5 crystal coupled to lumped element resonators at millikelvin temperatures [5]. The strong coupling regime with gens/2π ≈ 40 MHz and γ/2π ≈ 12 MHz has been reached for spin transitions with a g-factor below 2.


[1] J. Clarke and F. Wilhelm, Nature (London) 453, 1031 (2008)
[2] Y. Kubo et al., Phys.Rev.Lett. 107, 220501 (2011)
[3] R. Amsüss et al., Phys.Rev.Lett. 107, 060502 (2011)
[4] P. Bushev et. al., Phys. Rev. B 84, 060501 (R) (2011)
[5] S. Probst et. al., arXive: 1212.2856 (2012)