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Experimental work on entangled photon holes

Experimental work on entangled photon holes. T.B. Pittman, S.M. Hendrickson, J. Liang, and J.D. Franson UMBC ICSSUR Olomouc, June 2009. Experimental work on entangled photon holes. T.B. Pittman, S.M. Hendrickson, J. Liang, and J.D. Franson UMBC ICSSUR Olomouc, June 2009.

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Experimental work on entangled photon holes

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  1. Experimental work on entangled photon holes T.B. Pittman, S.M. Hendrickson, J. Liang, and J.D. Franson UMBC ICSSUR Olomouc, June 2009

  2. Experimental work on entangled photon holes T.B. Pittman, S.M. Hendrickson, J. Liang, and J.D. Franson UMBC ICSSUR Olomouc, June 2009 Linear Optics Quantum Computing, Zeno Gates Entangled-Photon Holes

  3. Outline • Entangled Photon holes? • Generation of these states by • two-photon absorption • quantum interference • Experimental observation of photon holes using quantum interference • Towards Bell’s inequality tests

  4. Optical Entanglement • Entanglement of photon pairs: • polarization • momentum • …. • ….combinations of properties • We are investigating a new form of entanglement • arises from the absence of photon pairs themselves • correlated absences…. “Entangled photon holes” Polarization entanglement from Type II PDC (Kwiat ‘95)

  5. Creation of entangled photon holes can have macroscopic effects on two-photon absorption • effects of entanglement can be observed with “classical detector” • This talk will focus instead on the basic concept and recent experimental work

  6. What are entangled photon holes? • First, consider photon pairs from typical PDC scenario: • Photons generated at same time, but that time is uncertain • superposition of these times  entanglement • background in each beam is empty • but uniform probability amplitude to find photon pair anywhere parametric down-conversion

  7. What are entangled photon holes? Two-photon absorption medium • Now consider ideal two-photon absorption • Photons annihilated at same time, but that time is uncertain • superposition of these times  entanglement • Background in each beam is constant • But uniform probability amplitude to find hole pair anywhere weak coherent state inputs

  8. Consider two single-photon inputs “holes” correlated in time, but could be generated at any time: coherent superposition

  9. PDC with narrowband pump photon pair could be produced at any time coherent superposition of these times

  10. Photon pairs vs. Photon holes • Entangled photon holes: “negative image” of PDC • empty background • photon pair anywhere • constant background • hole pair anywhere

  11. Ideal two-photon absorption? • Generation of entangled photon holes in this way requires strong two-photon absorption at the single-photon level • Very difficult to achieve (works in progress) • example system: tapered optical fiber in atomic vapor • Can entangled photon holes be generated through quantum interference instead? • Yes

  12. TPA in tapered optical fibers Rb atoms optical fiber evanescent field outside fiber • “heat and pull”: sub-wavelength diameter wires • evanescent field interacts with Rubidium vapor Reduced mode volume beats optimal free-space focusing (for TPA)

  13. Recent experiments with tapered optical fibers in Rb taper: d ~ 450 nm(over L ~ 5 mm) d ~ 125 mm • gives ~106 improvement in TPA rateover focused beam • even this is way too small for observingTPA at single-photon levels!H.You et.al. PRA 78, 053803 (2008)

  14. Side note: nonlinear transmission through TOF Nonlinear transmission • Rb atoms tend to accumulate on TOF • Reduces transmission (scattering) • can be removed using optical beam propagating through the TOF • probably LIAD & thermal effects • results in nonlinear transmission % saturation spectroscopy S.M. Hendrickson et.al. JOSA B 26, 267 (2009) S. Spillane et.al PRL 100, 233602 (2008)

  15. Photon holes via quantum interference ? Interference effect to suppress the probability P11 of finding one photon in each output mode?

  16. Photon holes via quantum interference Interference effect to suppress the probability P11 of finding one photon in each output mode? mix with phase-locked PDC source at 50/50 BS Note:TPA case: classical in  nonlinearity  quantum out this case: classical in + quantum in  interference  quantum out

  17. Photon holes via quantum interference • If indistinguishable amps and f = p, destructive interference (P11 = 0) • suppress any pairs from “splitting” at 50/50 • leaves photon hole pairs in constant laser background • experimental challenge: how to phase-lock PDC & weak laser? • answer: Koashi et.al. phase-coherence experiment (1994) what is P11 ?

  18. frequency-doubled laser (2w)for PDC pump  PDC pairs at w • fundamental (w) as weak coherent state • MZ-like interferometer  phase f

  19. Koashi et.al. PRA (1994) Lu and Ou, cw experiment PRL 88, 023601 (2002) Resch et.al. two-photon switch PRL 87, 123603 (2001) Versatile method: many implementations possible… Kuzmich et.al. homodyned Bell-test PRL 85, 1349 (2000)

  20. PDC laser “HOM” beam splitter crystal SHG pick - off delay primary filter beam splitter mode - locked PDC APD - 2 laser f APD - 1 ND delay laser PBS stop filters l - plate start data aq . TAC Photon holes experiment

  21. PDC laser “HOM” beam splitter crystal SHG pick - off delay primary filter beam splitter mode - locked PDC APD - 2 laser f APD - 1 ND delay laser PBS stop filters l - plate start data aq . TAC Photon holes experiment “HOM dip” V~99%

  22. PDC laser “HOM” beam splitter crystal SHG pick - off delay primary filter beam splitter mode - locked PDC APD - 2 laser f APD - 1 ND delay laser PBS stop filters l - plate start data aq . TAC Photon holes experiment “HOM dip” V~99% giant MZ interferometer (fiber and free-space) key point: phase f

  23. step 1: calibration matched two-photon amplitudes weak laser only (76 MHz pulse train) PDC only coincidence counts relative delay (ns)

  24. step 2: phase control f= 0o f= 180o Visibility ~90%

  25. step 3: observation of photon holes Probability of finding one photon in each beam is suppressed Note: not completely eliminated. due to imperfect mode-matching Pittman et.al. PRA 74, 041801R (2006)

  26. Data summary laser only PDC only main result

  27. Data summary • Important: data collected shows existence of photon holes, but does not demonstrate entangled nature of state--analogous to just measuring “photon pairs” in, say, Kwiat ’95 polarization experiments • additional measurements are required: -- Bell test with entangled photon holes laser only PDC only main result

  28. Bell’s inequality tests basic idea: use “Franson interferometer” • PDC source • only S1S2 and L1 L2 amplitudes • can be used to violate Bell’s ineq.

  29. Bell’s inequality tests basic idea: use “Franson interferometer” • PDC source • only S1S2 and L1 L2 amplitudes • can be used to violate Bell’s ineq. • photon holes source • Photons never emitted at same time • only S1L2 and L1S2 amplitudes

  30. Bell’s inequality tests • Interpretation is difficult: detectors only register background photons -- photon holes suppress detection process in a nonlocal way basic idea: use “Franson interferometer” • PDC source • only S1S2 and L1 L2 amplitudes • can be used to violate Bell’s ineq. • photon holes source • Photons never emitted at same time • only S1L2 and L1S2 amplitudes

  31. Time-bin entangled photon holes • Photon hole generation: relies on interference of independent sources • short-pulsed lasers/narrowband filters for indistinguishability • no cw “energy-time” type entanglement • this puts our Bell test exp’s into the “time-bin” regime (Gisin’s group) • Experiments currently underway (4 stabilizations req’d)

  32. photon hole source Time-bin entangled photon holes • Photon hole generation: relies on interference of independent sources • short-pulsed lasers/narrowband filters for indistinguishability • no cw “energy-time” type entanglement • this puts our Bell test exp’s into the “time-bin” regime (Gisin’s group) • Experiments currently underway (4 stabilizations req’d)

  33. Summary and outlook • New form of entanglement • entangled photon holes • “negative image” of PDC • Generation via ideal TPA or quantum interference effects • recent experiments • Many open questions: • … • quantum communications • …

  34. Some comments on photon hole data • Data looks similar to that typically obtained by splitting a conventional anti-bunched state • But that kind of (two-beam) state is very different than photon hole states of interest here excitation pulse train statistics of either beam resemble a coherent state splitting an antibunched beam gives two antibunched states • >> also different than the (single-mode) states produced by “hole-burning” in Fock space: B. Basiea et.al. Phys. Lett A 240, 277 (1998) • >> and not the same as the two-mode single-photon states of the form |0,1> + | 1,0>

  35. (HISTORICAL SIDE NOTE) • 1st demo that required “Multi-photon” experimental conditions • Ultra-fast pulsed-PDC and narrow-band filters for indistinguishability • now used for many experiments Bouwmeester et.al. Teleporation Nature 390, 575 (1997) Koashi et.al. PDC phase coherence PRA 50, R3605 (1994) Rarity et.al. PDC & |a> Philos. Trans. 355, 2567 (1997)

  36. primary beam splitter HOM & primary beam splitters PDC photons weak laser pulse HOM beam splitter Fiber-based interferometer

  37. Rb TPA frequency-locking system

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