Large conditional single-photon crossphase modulation

Kristin M. Beck, Mahdi Hosseini, Yiheng Duan, Vladan Vuletić*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

60 Scopus citations


Deterministic optical quantum logic requires a nonlinear quantum process that alters the phase of a quantum optical state by π through interaction with only one photon. Here, we demonstrate a large conditional cross-phase modulation between a signal field, stored inside an atomic quantum memory, and a control photon that traverses a high-finesse optical cavity containing the atomic memory. This approach avoids fundamental limitations associated with multimode effects for traveling optical photons. We measure a conditional cross-phase shift of π=6 (and up to π=3 by postselection on photons that remain in the system longer than average) between the retrieved signal and control photons, and confirm deterministic entanglement between the signal and control modes by extracting a positive concurrence. By upgrading to a state-of-the-art cavity, our system can reach a coherent phase shift of π at low loss, enabling deterministic and universal photonic quantum logic.

Original languageEnglish (US)
Pages (from-to)9740-9744
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number35
StatePublished - Aug 30 2016


  • Cavity quantum electrodynamics
  • Cross-phase modulation
  • Electromagnetically induced transparency
  • Photonic quantum gate
  • Single-photon kerr nonlinearity

ASJC Scopus subject areas

  • General


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