Broadband energy entangled photons and their potential for space applications. André Stefanov University of Bern, Switzerland

Transcription

1 Broadband energy entangled photons and their potential for space applications André Stefanov University of Bern, Switzerland Quantum Technology in Space, Malta,

2 SPDC for quantum communication SPDC i s Spontaneous parametric downconversion Easy High quality of states Losses limit the maximal distance Increase the pair production rate Increase the information capacity / pair 2/24

3 Outlook Energy-time photonic entanglement Experimental spectral manipulation Quantum Information protocols, Bell Inequalities Ultrafast measurements with CW light Conclusion, going to space 3/24

4 Photonic entangled qudits SPDC i s Polarization entanglement Transverse momentum Energy entanglement 4/24

5 Broadband energy-entangled photons Combine high temporal resolution with high energy resolution Join spectral amplitude Join temporal amplitude p Classical light Entangled light 5/24

6 Entropy of Entanglement Quantify the entanglement of the state Entropy of the subsystem Numerical computation CW pump field large discretized matrices: Compute E without diagonalization of A : maximally entangled qudit with T.P. Wihler, B. Bessire, A.S. Journal of Physics A,47(24), (2014). 6/24

7 Outlook Energy-time photonic entanglement Experimental spectral manipulation Quantum Information protocols, Bell Inequalities Ultrafast measurements with CW light Conclusion, going to space 7/24

8 Experiment Setup Preparation (SPDC) Manipulation Detection (SFG) Beam dump Spatial light modulator (SLM) Bandpass filter 532 nm SPCM PPKTP PPKTP Detected signal after the SFG process: 5 W pump laser 1064 nm 1 µw 4-prism compressor: Compensate for dispersion Align the spectrum Jenoptik S640d Sensitive to a phase in the SLM transfer function Complex transfer function: A. Pe er, B. Dayan, A. A. Friesem, and Y. Silberberg, Phys. Rev. Lett. 94, (2005) 1000 s -1 up-converted photons

9 Frequency-bins Maximally entangled qutrit In general 9/24

10 Quantum State tomography Detected signal is equivalent to the signal of a projective measurement with Reconstruction of density matrices for maximally entangled qudits by Maximum Likelihood Estimation C. Bernhard, et al., PRA, 88, 3, (2013) 10/24

11 Collins-Gisin-Linden-Massar-Popescu (CGLMP) inequality Alice S Bob Alice S Bob where the above probabilities are sums of joint probabilities given by D. Collins, et. al., Phys. Rev. Lett. 88, (2002) 11/24

12 CGLMP inequalities (with frequency-bins) A non-maximally entangled qutrit state violates CGLMP stronger than a maximally entangled qutrit 2-qubit state with a : 2-qutrit state with a : S. Schwarz, et al. (2015). IJQI, 12, /24

13 Multisettings Bell Scenario Alice S Bob Some multisettings Bell inequalities can be maximally violated already with entangled two-qubit states 13/24

14 2-party, 3-Input, 3-Output Bell scenario Maximally violated by maximally entangled qutrits Maximally violated by entangled qubits S. Schwarz, et al. NJP, 18(3), (2016) 14/24

15 Time shift between signal and idler phase idler amplitude time signal amplitude idler signal time 15/24

16 Sensitivity to dispersion Two photon correlation function Y(t) 2 Fourier transform of G( ) Propagates like a fs pulse but CW Dispersion No dispersion 16/24

17 Dispersion cancellation by entanglement Minimal broadening of the arrival time difference minimal broadening separable states photon 1 is the width of 17/24

18 Measure of G (2) Target function is expressed by two signals 18/24

19 Violation of classical inequality No broadening observed Violation of minimal broadening S.Lerch, et al., JOSA B, 50, (2017) 19/24

20 From entanglement to classical correlation phase Entangled two-photon state Random phase at SLM destroy fixed phase relation (coherence) between signal and idler signal idler 0 State becomes a weighted mixture Quantum correlations Classical correlations 20/24

21 From entanglement to classical correlation Arrival time difference between signal and idler 21/24

22 Outlook Energy-time photonic entanglement Experimental spectral manipulation Quantum Information protocols, Bell Inequalities Ultrafast measurements with CW light Conclusion, going to space 22/24

23 Conclusion, going to space Broadband entangled photons High temporal resolution Large dimensional entanglement Futur: High rate single photon detection with fs resolution Non-local detection with fs timing resolution Increase the duty cycle by space-time coupling 23/24

24 Ackowledgement B. Bessire C. Bernhard S. Lerch S. Schwarz M. Unternährer J. Kohn Collaborators: T. P. Wihler (Bern) P. Lauber (AIUB, Bern) Thank you for your attention! S. Wolf, A. Montina (Lugano) F. Scheffold (Fribourg) Y.-C. Liang (Taiwan) 24/24