Control of the conformations of ion Coulomb crystals in a Penning trap

Abstract

Laser-cooled atomic ions form ordered structures in radiofrequency ion traps and in Penning traps. Here we demonstrate in a Penning trap the creation and manipulation of a wide variety of ion Coulomb crystals formed from small numbers of ions. The configuration can be changed from a linear string, through intermediate geometries, to a planar structure. The transition from a linear string to a zigzag geometry is observed for the first time in a Penning trap. The conformations of the crystals are set by the applied trap potential and the laser parameters, and agree with simulations. These simulations indicate that the rotation frequency of a small crystal is mainly determined by the laser parameters, independent of the number of ions and the axial confinement strength. This system has potential applications for quantum simulation, quantum information processing and tests of fundamental physics models from quantum field theory to cosmology.

Rapid crystallization of externally produced ions in a Penning trap

“…When the laser cooling reduces the kinetic energy of the confined ions sufficiently, they "freeze" in the effective potential given by the trap and their mutual Coulomb interactions, as has been demonstrated in numerous experiments; see, for example, [7,8,[20][21][22][23][24].…”

“…Laser cooling of the stored 24 Mg + ions is achieved on the red-detuned side of the 279.55-nm 2 S1/2 → 2 P3/2 transition with a natural linewidth of = 2π × 41.8 × 10 6 s −1 [34]. Frequency quadrupling of light from a commercial infrared fiber laser produces the required light with a spectral width of less than 1 MHz and a few tens of milliwatts of maximum power.…”

“…For a 24 Mg + ion in the present trap with a characteristic size d = 7.062 mm, a well-depth efficiency parameter C 2 = 0.578, and at a trapping voltage of U = 50 V, these frequencies are ω z = 2π × 241.4 kHz, ω − = 2π × 11.4 kHz, and ω + = 2π × 2.55 MHz. Equation (6) holds true as long as the Debye length…”

“…The geometric properties of ion plasmas and the formation of ion Coulomb crystals have been described in detail, for example, in [7,8,[20][21][22][23][24]46,[49][50][51][52]. For the present ion numbers of the order of 1 × 10 3 to 1 × 10 5 ("mesoscopic"), and aspect ratios (axial extension to radial extension) of typically α 1, the so-called planar-shell model is a good approximation to describe the geometry of the confined plasmas.…”

Trapped-ion quantum error-correcting protocols using only global operations

“…We consider a six-ion Coulomb crystal in a Penning trap [14] as depicted in Fig. 1, and we provide a protocol to encode an arbitrary quantum state to either the five-qubit code (5QC) [15], or the five-qubit repetition code (5RC).…”