Paula - Linear Quantum-Spin Systems

Research Overview	Crystal Kinks		QSim Bermuda	TIAMO Ba+Rb	TIAMO Ba+Li
		QSim Paula

Matthias Wittemer, Jan-Philipp Schröder, Frederick Hakelberg, Philip Kiefer, Ulrich Warring, and Tobias Schaetz

quantum simulation with trapped ions

    Richard Feynman originally proposed to use a well-controlled quantum system to efficiently tackle problems that are too complex to be addressed with classical computers, such as quantum dynamics of many body systems; he called his hypothetical device a quantum computer (QC). Today, we classify it as an analog quantum simulator (AQS) to distinguish it from a QC, in which the dynamics of a system are implemented via algorithms of gate operations on subsets of qubits. In an AQS the strategy is to adiabatically evolve a quantum system from an experimentally well-prepared (initial) state to a new state by changing its Hamiltonian in a controlled manner, to reveal, for example, highly non-trivial dynamics, such as quantum phase transitions. Either device, QC and AQS, may help to develop insights into underlying physics. In addition, well-controlled quantum systems may enable to simulate processes in quantum chemistry and (quantum) biology, such as photosynthesis, where it is under debate whether the laws of quantum mechanics could also influence biological and other macroscopic objects. In any cases, we may gain a deeper understanding of the essential ingredients by directly observing a controlled model quantum system.

laser cooled trapped ions form complex 3D (cp. KINKS) and more simple linear Coulomb crystals

    Currently there are efforts to implement QC/AQS in many different physical systems; we purse an approach with trapped ions: In the past, spectacular progress has been achieved in controlling the dynamics of such isolated quantum systems, as highlighted with the award of the 2012 Physics Nobel Prize to S. Haroch and D. J. Wineland: ”for ground-breaking experimental methods that enable measuring and manipulation of individual quantum systems” [Nobel prize website]. Nonetheless such controlled quantum systems (cp. tools below) have been limited to only a few constituents to permit mitigating residual decoherence effects. Methods for implementing large-scale devices/systems are still in the developmental phase. One of our goals is to contribute to a substantially more robust implementation of such systems to enable and to drive progress toward larger quantum systems (cp. BERMUDA project). While another mission of the PAULA apparatus is to study couplings of isolated quantum systems to well-controlled environments (open-quantum systems).

 

  

impressions from a quantum simulator: ion trap, dye-laser system, and second-harmonic-generation stage

    In the past, PAULA has been used to demonstrate the first optical trap for ions (now a dedicated spin-off project: OPIAT) and proof-of-principle quantum simulation experiments, e.g.: simulation of a quantum phase transition [Nature Physics 4, 757 - 761 (2008)] and quantum walk [Phys. Rev. Lett. 103, 090504 (2009)].

our tools in the lab

conventional linear Paul trap for linear ion chains segmented electrodes for loading and experimental zones    characteristic trap scale/width r0 ≈ 800 µm and 400 µm  rf drive frequency Ωrf /(2 π) ≈ 56 MHz  motional frequencies: ωax /(2 π) ≈ 0.5-2.5 MHz (axial) and ωrad /(2 π) ≈ 3.5-5.5 MHz (radial) trap depth of >1 eV   full quantum control via Raman beams and microwaves (cp. below)

full control over Internal and motional degree of freedom Doppler cooling and optical pumping into the long-lived hyperfine/Zeeman state of the 2S1/2 fine-structure manifold high-fidelity control of the electronic (internal) degree of freedom with microwaves or Raman beams coupling to the motion with Raman beams tuned to motional sidebands of spin-carrier transitions   state read-out by fluorescence from a state-selective cycling transition

 

further reading

 

• Measurement of quantum memory effects and its fundamental limitations 
  M. Wittemer, G. Clos, H.-P. Breuer, U. Warring, T. Schaetz
  Phys. Rev. A 97, 020102(R) (2018) - arXiv: 1702.07518 (2017)
• The new thermodynamics: how quantum physics is bending the rules
  Nature 551, 20–22 (2017)

• Time-resolved observation of thermalization in an isolated quantum system
  G. Clos, D. Porras, U. Warring, T. Schaetz
  Phys. Rev. Lett. 117, 170401 (2016) - arXiv: 1509.07712 (2015)
• Decoherence-assisted spectroscopy of a single Mg+ ion 
  G. Clos, M. Enderlein, U. Warring, T. Schaetz, D. Leibfried
  Phys. Rev. Lett. 112, 113003 (2014) - arXiv:1402.1678 (2014)
• Quantum walk with non-orthogonal position states 
  R. Matjeschk, A. Ahlbrecht, M. Enderlein, Ch. Cedzich, A. H. Werner, M. Keyl, T. Schaetz, R. F. Werner
  Phys. Rev. Lett. 109, 240503 (2012) - arXiv:1206.0220 (2012)
• Experimental simulation and limitations of quantum walks with trapped ions 
  R. Matjeschk, Ch. Schneider, M. Enderlein, T. Huber, H. Schmitz, J. Glueckert, T. Schaetz
  New J. Phys. 14, 035012 (2012) - arXiv:1108.0913 (2011)
• Quantum Odyssey of Photons 
  T. Schaetz, Ch. Schneider, M. Enderlein, T. Huber and R. Matjeschk 
  ChemPhysChem 12, 71-74 (2011)
• The quantum Walk of a trapped Ion in phase space 
  H. Schmitz, R. Matjeschk, Ch. Schneider, J. Glueckert, M. Enderlein, T. Huber and T. Schaetz
  Phys. Rev. Lett. 103, 090504 (2009)
  - pdf 
  - Pressemitteilung 
  - arXiv:0904.4214 
  - APS-Synopsis: Quantum walking the line 
  - Selected for Virtual Journal of Quantum Information
• The 'arch' of simulating quantum spin systems with trapped ions  
  H. Schmitz, A. Friedenauer, Ch. Schneider, R. Matjeschk, M. Enderlein, T. Huber, J. Glueckert, D. Porras and T. Schaetz 
  Appl. Phys. B 95, 195 (2009)
• Simulating a quantum magnet with trapped ions 
  A. Friedenauer, H. Schmitz, J. Glueckert, D. Porras and T. Schaetz
  Nature Physics 4, 757 - 761 (2008)
  - pdf 
  - Pressemitteilung 
  - arXiv:0802.4072v1 (pdf) 
  - ScienceNews (174, 5, August the 30th)