IQsim13 talk [PPTX 6.22MB]
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Seb Weidt IQsim13, Brighton IQT group, University of Sussex ο½ Linear Paul trap Drive frequency: 2π x 20 MHz Ion-electrode separation: 310 μm π£π₯,π¦ /2π = 0.5 − 2.5 MHz π£π§ /2π = 0.05 − 1 MHz ο½ Cooling 171Yb+ F=0 3 D[3/2]1/2 2 GHz F=1 2P F=1 1/2 F=0 F=2 2D 1 GHz 3/2 F=1 369nm 2S F=1 1/2 12.6 GHz 935nm F=0 ο½ Cooling 171Yb+ F=0 3 D[3/2]1/2 2 GHz F=1 2P F=1 1/2 F=0 F=2 2D 1 GHz 3/2 F=1 369nm 2S F=1 1/2 12.6 GHz 935nm F=0 ο½ State preparation F=0 3 D[3/2]1/2 2 GHz F=1 2P F=1 1/2 2 GHz F=0 F=2 2D 1 GHz 3/2 F=1 369nm 2S 935nm F=1 1/2 F=0 Optical pumping to 2S1/2 F=0 in ~ 20 μs ο½ Coherent manipulation F=0 3 D[3/2] F=1 2P F=1 1/2 F=0 F=2 F=1 2S F=1 1/2 12.6 GHz F=0 2D 3/2 1/2 ο½ State detection 3D[3/2] 2P F=1 1/2 2D 3/2 F=1 1/2 935nm F=0 369nm 2S 1/2 F=0 2 GHz F=1 F=0 F=2 1 GHz F=1 ο½ State detection 3D[3/2] 2P F=1 1/2 2D 3/2 F=1 1/2 935nm F=0 369nm 2S 1/2 F=0 2 GHz F=1 F=0 F=2 1 GHz F=1 ο½ State detection 3D[3/2] 2P F=1 1/2 2D 3/2 F=1 1/2 935nm F=0 369nm 2S 1/2 F=0 2 GHz F=1 F=0 F=2 1 GHz F=1 ο½ State detection Threshold technique Detection fidelity ~ 0.93 Increase collection efficiency for improvement ο½ Ground state F=1, mF = +1 ππ΅ + F=1, mF = 0 ππ΅ − F=1, mF = -1 2S π0 1/2 π0 = 2π × 12.6 GHz ππ΅ F=0, mF = 0 ± ππ΅ = π΅ β Typical applied B ~ 10 Gauss → ππ΅ = 2π × 14 MHz ο½ Ground state ππ΅ + ππ΅ − 2S 1/2 π0 π0 = 2π × 12.6 GHz ππ΅ ± ππ΅ = π΅ β Typical applied B ~ 10 Gauss → ππ΅ = 2π × 14 MHz ο½ Ground state ππ΅ + ππ΅ − 2S 1/2 π0 π0 = 2π × 12.6 GHz ππ΅ ± ππ΅ = π΅ β Typical applied B ~ 10 Gauss → ππ΅ = 2π × 14 MHz ο½ Motional coupling with a magnetic field gradient Add a magnetic field gradient Gives a state dependent force Effective Lamb-Dicke parameter ππππ = 1.19 × 3 −2 −1 6 10 ππ π ππ§ π΅ 3 π£π§ 2 ππ§ π΅ = 20 T/m, π£π§ /2π = 100 kHz ⇒ ππππ = 0.04 Requires the use of magnetic field sensitive states F. Mintert and C. Wunderlich, Phys. Rev. Lett. 87, 257904 (2001) A. Kromova et al., Phys. Rev. Lett. 108, 220502 ππ΅ + ππ΅ − π0 Fluctuations in the magnetic field causes dephasing Gives rise to short coherence times ο½ Rabi oscillations using magnetic field sensitive state Fluctuations in the magnetic field causes dephasing coherence time of ~ 500 μs ο½ Dressed-states Two microwave dressing fields ππ΅ + ππ΅ − Ωππ€ Ωππ€ − + π0 + − When Ωππ€ = Ωππ€ = Ωππ€ : Three eigenstates: N. Timoney, I. Baumgart, M. Johanning, A. F. Varon, M. B. Plenio, A. Retzker, and C. Wunderlich, Nature 476, 185 (2011) ο½ Dressed qubit 2 Ωππ€ Three eigenstates: N. Timoney, I. Baumgart, M. Johanning, A. F. Varon, M. B. Plenio, A. Retzker, and C. Wunderlich, Nature 476, 185 (2011) ο½ Dressed qubit 2 Ωππ€ Form a qubit using and Insensitive to magnetic field fluctuations apart from at the splitting frequency Ωππ€ 2 Insensitive to microwave power fluctuations N. Timoney, I. Baumgart, M. Johanning, A. F. Varon, M. B. Plenio, A. Retzker, and C. Wunderlich, Nature 476, 185 (2011) ο½ Preparation Prep Optical pumping to prepare S. C. Webster, S. Weidt, K. Lake, J. J. McLoughlin and W. K. Hensinger, Phys. Rev. Lett. 111, 140501 (2013) ο½ Preparation Prep π to Microwave π-pulse to S. C. Webster, S. Weidt, K. Lake, J. J. McLoughlin and W. K. Hensinger, Phys. Rev. Lett. 111, 140501 (2013) ο½ Preparation Prep π to STIRAP Partial STIRAP - Bare states mapped to dressed-states Ωππ€ Ωππ€ − + Ωππ€ π‘ th S. C. Webster, S. Weidt, K. Lake, J. J. McLoughlin and W. K. Hensinger, Phys. Rev. Lett. 111, 140501 (2013) ο½ Preparation Prep π to STIRAP Partial STIRAP - Bare states mapped to dressed-states Ωππ€ Ωππ€ − + Ωππ€ π‘ th S. C. Webster, S. Weidt, K. Lake, J. J. McLoughlin and W. K. Hensinger, Phys. Rev. Lett. 111, 140501 (2013) ο½ Preparation Prep π to STIRAP Partial STIRAP - Bare states mapped to dressed-states Ωππ€ Ωππ€ − + Ωππ€ π‘ th Peak Ωππ€ /2π 25 kHz Pulse width 450 μs Pulse separation 356 μs Ωππ€ /2π during hold 16 kHz S. C. Webster, S. Weidt, K. Lake, J. J. McLoughlin and W. K. Hensinger, Phys. Rev. Lett. 111, 140501 (2013) ο½ Detection Prep π to STIRAP Partial STIRAP - Bare states mapped to dressed-states Ωππ€ Ωππ€ − + Ωππ€ π‘ th S. C. Webster, S. Weidt, K. Lake, J. J. McLoughlin and W. K. Hensinger, Phys. Rev. Lett. 111, 140501 (2013) ο½ Detection Prep π to STIRAP π to Microwave π-pulse to followed by state detection S. C. Webster, S. Weidt, K. Lake, J. J. McLoughlin and W. K. Hensinger, Phys. Rev. Lett. 111, 140501 (2013) ο½ Lifetime measurement Ωππ€ π‘ Ωππ€ Ωππ€ th + − Lifetime of = 550 ms S. C. Webster, S. Weidt, K. Lake, J. J. McLoughlin and W. K. Hensinger, Phys. Rev. Lett. 111, 140501 (2013) ο½ Qubit manipulation Second order Zeeman shift ππ΅ + Significant non-linear Zeeman shift for small Bππ΅ − fields (ππ΅ + ≠ ππ΅ − ) Ωππ Ωππ€ Ωππ€ − 10 Gauss – 31 kHz + π0 One rf field coupling to will drive to as long as Ωππ << Ωππ€ S. C. Webster, S. Weidt, K. Lake, J. J. McLoughlin and W. K. Hensinger, Phys. Rev. Lett. 111, 140501 (2013) ο½ Rabi oscillations Ωππ /2π 1.4 kHz Dressed coherence time 500 ms Bare coherence time 500 μs S. C. Webster, S. Weidt, K. Lake, J. J. McLoughlin and W. K. Hensinger, Phys. Rev. Lett. 111, 140501 (2013) ο½ Ramsey experiment Arbitrary qubit rotations are possible Detuned π/2 pulse Free precession Detuned π/2 pulse S. C. Webster, S. Weidt, K. Lake, J. J. McLoughlin and W. K. Hensinger, Phys. Rev. Lett. 111, 140501 (2013) ο½ Creating a magnetic field gradient Four Samarium Cobalt permanent magnets ο½ Individual addressing in frequency space Magnetic field strength βπ βπ π0 ο½ Individual addressing in frequency space βπ = 2.03 MHz Ion 1 s 6 μm π£π§ /2π 437 kHz ππ§ π΅ 24 T/m ππππ 0.004 Ion 2 βπ βπ ο½ Individual addressing in frequency space βπ = 2.03 MHz Ion 1 s 6 μm π£π§ /2π 437 kHz ππ§ π΅ 24 T/m ππππ 0.004 Ion 2 βπ βπ ο½ Individual addressing in frequency space βπ = 2.03 MHz Ion 1 s 6 μm π£π§ /2π 437 kHz ππ§ π΅ 24 T/m ππππ 0.004 Ion 2 βπ βπ ο½ Resolving motional sidebands π£ Ωππ€ /2π (carrier) / (sideband) 50 kHz / 8 kHz π£π§ /2π 168 kHz ππ§ π΅ 24 T/m ππππ 0.019 ο½ Creation of Schrödinger cat state Apply Mølmer-Sørensen type spin operator + = 1 2 +1 + π ππ 0 , − = 1 2 −π −ππ +1 − 0 πΏ Driving detuned red and blue sideband -πΏ Coherent states will be displaced in phase space Im(α) + ππππ Ωππ πΌ π‘ = 1 − π −ππΏπ‘ 2πΏ 1 1 −2 πΌ π 0 = 1−π 2 π‘ 2 Re(α) − First demonstrated by Monroe et al. Science 272, 1131 K. Mølmer and A. Sørensen, Phys. Rev. Lett, 82:1835-1838, 1999 ο½ Creation of Schrödinger cat state πΏ -πΏ t 120 μs Ωππ€ /2π 41 kHz π£/2π 267 kHz ππππ 0.009 ο½ Creation of Schrödinger cat state No interference between wave packets Im(α) Re(α) t 120 μs Ωππ€ /2π 41 kHz π£/2π 267 kHz ππππ 0.009 ο½ Creation of Schrödinger cat state Interference between wave packets Im(α) Re(α) t 120 μs Ωππ€ /2π 41 kHz π£/2π 267 kHz ππππ 0.009 ο½ Creation of Schrödinger cat state Two-ion gate time ~ 15 ms Coherence time ~ 500 μs Combine magnetic field gradient with dressed-state setup t 120 μs Ωππ€ /2π 41 kHz π£/2π 267 kHz ππππ 0.009 ο½ Dressed-state motional coupling ππ΅ + Ωππ ππ΅ − Ωππ€ Ωππ€ − + π0 Use rf field to drive motional sidebands in dressed-state qubit ο½ Dressed-state motional coupling π· → 0′ Ωππ Ωππ€ Ωππ€ + − Ωππ€ /2π (carrier) / (sideband) 7 kHz / 1 kHz π£π§ /2π 267 kHz Gradient 24 T/m ππππ 0.009 ο½ Dressed-state motional coupling π → π+1 π· → 0′ Ωππ Ωππ€ Ωππ€ + − Ωππ€ /2π (carrier) / (sideband) 7 kHz / 1 kHz π£π§ /2π 267 kHz Gradient 24 T/m ππππ 0.009 ο½ Dressed-state motional coupling π → π+1 π → π−1 π· → 0′ Ωππ Ωππ€ Ωππ€ + − Ωππ€ /2π (carrier) / (sideband) 7 kHz / 1 kHz π£π§ /2π 267 kHz Gradient 24 T/m ππππ 0.009 ο½ Dressed-state motional coupling π → π+1 π → π−1 π· → 0′ Ωππ Ωππ€ Ωππ€ π → π + − Ωππ€ /2π (carrier) / (sideband) 7 kHz / 1 kHz π£π§ /2π 267 kHz Gradient 24 T/m ππππ 0.009 ο½ Dressed-state motional coupling π → π+1 π → π−1 π· → 0′ π → π Ωππ Ωππ€ Ωππ€ + − Ωππ€ /2π (carrier) / (sideband) 7 kHz / 1 kHz π£π§ /2π 267 kHz Gradient 24 T/m ππππ 0.009 ο½ Dressed-state motional coupling π → π−1 π → π+1 π → π−1 π· → 0′ π → π Ωππ Ωππ€ Ωππ€ + − Ωππ€ /2π (carrier) / (sideband) 7 kHz / 1 kHz π£π§ /2π 267 kHz Gradient 24 T/m ππππ 0.009 ο½ Dressed-state motional coupling Ωππ Ωππ€ Ωππ€ π → π−1 π → π+1 π → π+1 π → π−1 π· → 0′ π → π + − Ωππ€ /2π (carrier) / (sideband) 7 kHz / 1 kHz π£π§ /2π 267 kHz Gradient 24 T/m ππππ 0.009 ο½ Dressed-state motional coupling Ωππ Ωππ€ Ωππ€ π → π π → π−1 π → π+1 π → π+1 π → π−1 π· → 0′ + − Resilient to magnetic field fluctuations BUT sensitive to magnetic field gradient ο½ Arbitrary manipulation of magnetic field noise resilient dressed-state qubit ο½ Creation of a strong magnetic field gradient ο½ Individual addressing and motional coupling using bare states ο½ Creation of Schrödinger cat state ο½ Motional coupling using dressed-state qubit Head of Group: Dr. Winfried Hensinger Postdocs: Dr. Simon Webster Dr. Gouri Giri Research Assistants: Dr. Marcus Hughes Dr. James Siverns We gratefully acknowledge funding from: PhD Students: Seb Weidt Bjo Lekitsch Kim Lake Darren De Motte Joe Randall Eamon Standing David Murgia Tomas Navickas ο½ Ground state ππ΅ + ππ΅ − Magnetic field insensitive qubit Ωππ€ π0 ο½ Rabi oscillations Ωππ€ = 2π × 333 ππ»π§ Coherence time > 1s ο½ Creating a magnetic field gradient 10 mm Four Samarium Cobalt permanent magnets
