Srujan Meesala

Acceptor-induced bulk dielectric loss in superconducting circuits on silicon

  1. Zi-Huai Zhang,
  2. Kadircan Godeneli,
  3. Justin He,
  4. Mutasem Odeh,
  5. Haoxin Zhou,
  6. Srujan Meesala,
  7. and Alp Sipahigil
The performance of superconducting quantum circuits is primarily limited by dielectric loss due to interactions with two-level systems (TLS). State-of-the-art circuits with engineered
material interfaces are approaching a limit where dielectric loss from bulk substrates plays an important role. However, a microscopic understanding of dielectric loss in crystalline substrates is still lacking. In this work, we show that boron acceptors in silicon constitute a strongly coupled TLS bath for superconducting circuits. We discuss how the electronic structure of boron acceptors leads to an effective TLS response in silicon. We sweep the boron concentration in silicon and demonstrate the bulk dielectric loss limit from boron acceptors. We show that boron-induced dielectric loss can be reduced in a magnetic field due to the spin-orbit structure of boron. This work provides the first detailed microscopic description of a TLS bath for superconducting circuits, and demonstrates the need for ultrahigh purity substrates for next-generation superconducting quantum processors.
arxiv pdf

Non-classical microwave-optical photon pair generation with a chip-scale transducer

  1. Srujan Meesala,
  2. Steven Wood,
  3. David Lake,
  4. Piero Chiappina,
  5. Changchun Zhong,
  6. Andrew D. Beyer,
  7. Matthew D. Shaw,
  8. Liang Jiang,
  9. and Oskar Painter
Modern computing and communication technologies such as supercomputers and the internet are based on optically connected networks of microwave frequency information processors. In recent
years, an analogous architecture has emerged for quantum networks with optically distributed entanglement between remote superconducting quantum processors, a leading platform for quantum computing. Here we report an important milestone towards such networks by observing non-classical correlations between photons in an optical link and a superconducting electrical circuit. We generate such states of light through a spontaneous parametric down-conversion (SPDC) process in a chip-scale piezo-optomechanical transducer. The non-classical nature of the emitted light is verified by observing anti-bunching in the microwave state conditioned on detection of an optical photon. Such a transducer can be readily connected to a superconducting quantum processor, and serve as a key building block for optical quantum networks of microwave frequency qubits.
arxiv pdf