Continuous Variable Quantum ClusterState Generation Using a Tapered

Continuous. Variable Quantum Cluster-State Generation Using a Tapered Amplifier Andy Nicholas Black Miller Eaton Raphael Pooser Benjamin Lawrie ORNL is managed by UT-Battelle for the US Department of Energy

Table of Contents • What is a cluster-state? • What is one-way quantum computing? • What is a tapered amplifier? • Four-Wave Mixing • Squeezing and entanglement • Materials and Methods • Results • Conclusions 2 Large-Scale Cluster State Generation

What is a cluster-state? • Highly entangled multi-partite state. • Dual-rail cluster state [1, 2, 3]. Figure 1. Graph representation of a dual-rail cluster-state. • ω1 and ω2 are members of an EPR pair. • Edges are entangling interactions. 3 Large-Scale Cluster State Generation

What is one-way quantum computing? • Discrete-variable one-way quantum computing suffers from probabilistic entanglement generation [4, 5]. – Particles in micro-potential. • Continuous-variable one-way quantum computing offers deterministic entanglement generation [5]. – Entanglement of photons on a beam splitter. • Promises scalability due to ease in concurrent generation of large, entangled qubit states [2]. 4 Large-Scale Cluster State Generation

What is one-way quantum computing? • Comprised of measurement-based operations [4]. • Cluster-state is the substrate for data processing [4]. • Information input, processing, and retrieval is done by single particle measurements within state. • Quantum gates can be created by judicious measurement of cluster-state members [4]. 5 Large-Scale Cluster State Generation

What is a tapered amplifier? • Excited semi-conducting material used to amplifier a seed light source. Ridge-section Semiconductor Seed Output Heat sink Taper-section • Cost-effective alternative to Ti: Saph laser. • Suffers from spontaneous-emission—phase noise. – Important because phase noise can prevent observation of entanglement. 6 Large-Scale Cluster State Generation

More on tapered amplifiers. • Narrow spectral width output. • Output mode not Gaussian. – Image of the tapered amplifier chip. Figure 2. Example of tapered amplifier output mode [6]. 7 Large-Scale Cluster State Generation

Four-Wave Mixing • Third-order nonlinear interaction between input beams and amplification medium. – We used gaseous 85 Rb. 8 Large-Scale Cluster State Generation

Four-Wave Mixing • 9 Large-Scale Cluster State Generation

Squeezing and Entanglement • 10 Large-Scale Cluster State Generation

Materials and Methods • Experimental setup for measuring amplitude and phase variance: 11 Large-Scale Cluster State Generation

Results • Observed 4. 0 +/- 0. 1 d. B of intensity difference squeezing in output EPR pairs. • Phase sensitivity of noise level with vacuum input. ΔX_2 ΔP+2 Vacuum noise level 12 Large-Scale Cluster State Generation

Results • Inseparability value of I = 1. 47 +/- 0. 02 ΔX_2 ΔP+2 Vacuum noise level 13 Large-Scale Cluster State Generation

Conclusions • Intensity difference squeezing of single output pair— probe and conjugate—indicates EPR pairs were generated. • I = 1. 47 +/- 0. 02 satisfies necessary and sufficient condition for inseparability. • Possible to create four mode cluster state with a tapered amplifier. • Future research will characterize entanglement depth as tapered amplifier parameters are varied. 14 Large-Scale Cluster State Generation

Acknowledgements • This work was supported in part by the U. S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internship program. • We would like to thank Oak Ridge National Laboratory for SEED funding to begin this project. • I would like to thank Dr. Raphael Pooser and Dr. Benjamin Lawrie for guidance and fruitful discussions during the course of this research. • We would like to thank SESAPS for hosting this presentation. 15 Large-Scale Cluster State Generation

Thank You! 16 Large-Scale Cluster State Generation

References 1. S. Yokoyama et al. , ”Ultra-large-scale continuous-variable cluster states multiplexed in the time domain, ” Nature Photonics. 7, 982 -986 (2013). 2. M. Chen, N. C. Menicucci, and O. Pfister, “Experimental realization of multipartite entanglement of 60 modes of a quantum optical frequency comb, ” Phys. Rev. Lett. 112, 120505 -1 (2014). 3. N. Menicucci, “Temporal-mode continuous-variable cluster states using linear optics, ” Phys. Rev. A. 83, 062314 (2011). 4. R. Raussendorf and H. J. Briegel, “A one-way quantum computer, ” Phys. Rev. Lett. 86, 5188 -5191 (2001). 5. R. Pooser and J. Jing, “Continuous-variable cluster-state generation over the optical spatial mode comb, ” Phys. Rev. A. 90, 043841 -1 (2014). 6. “Tapered Amplifier Output Beam Output. ” Thorlabs. https: //www. thorlabs. com/newgrouppage 9. cfm? objectgroup_id=5336 7. Q. Glorieux, L. Guidoni, S. Guibal, J. Likforman, and T. Coudreau, “Strong quantum correlations in four wave mixing in 85 Rb vapor, ” Proc. of SPIE, 7727, 7727703 -1 (2010). 17 Large-Scale Cluster State Generation

References 8. L. Duan, G. Giedke, J. I Cirac, and P. Zoller, “Inseparability Criterion for Continuous Variable Systems, ” Phys. Rev. Lett. 84, 12 (2000). 18 Large-Scale Cluster State Generation