Short answer: Most trapped-ion quantum computers use radio-frequency traps, and microfabricated surface-electrode traps put the electrodes on a chip so ions can be held above it. Published experiments report trapping and shuttling ions in chip traps, and a 2024 paper reports a chip Penning trap that replaces the radio-frequency field with a 3 tesla magnetic field. All are laboratory demonstrations.
Why chips
A 2024 Nature paper says trapped ions in radio-frequency traps are among the leading approaches to quantum computers, because of high-fidelity gates and long coherence times. It lists challenges for scaling that come with radio frequencies: chips must tolerate high voltages, power dissipation must be managed, and the transport and placement of ions is restricted. A 2010 arXiv paper says individually trapped ions are a leading candidate for quantum information processing.
A planar trap, 2006
An early demonstration (arXiv quant-ph/0601173) shows ions confined in a radio-frequency Paul trap with a new geometry: electrodes in a single plane and ions held above it. The authors say the device uses a relatively simple fabrication procedure and has implications for manipulating large numbers of ions. They confine laser-cooled magnesium-24 ions about 40 micrometres above planar gold electrodes, measure motional frequencies and compare them with simulations. From escape times they determine a heating rate of about five motional quanta per millisecond at a trap frequency of 5.3 MHz.
A silicon-based trap, 2010
The 2010 paper presents the design, modelling and testing of surface-electrode traps built on a silicon substrate with silicon dioxide insulators and aluminium electrodes. The linear trap has symmetric radio-frequency leads, two interior DC electrodes and 40 individual lateral DC electrodes. Plasma-enhanced chemical vapour deposition grew silicon dioxide pillars to separate overhung aluminium electrodes from a ground plane. The authors report techniques for modelling control voltage solutions and the successful trapping and shuttling of ions in two identically constructed traps.
A chip Penning trap, 2024
The 2024 Nature paper realises a micro-fabricated Penning ion trap that removes the radio-frequency restrictions by using a 3 T magnetic field instead. The authors demonstrate full quantum control of an ion in this setting and the ability to transport the ion arbitrarily in the trapping plane above the chip. They say this opens a modification of the quantum charge-coupled device architecture with improved connectivity and flexibility, for large-scale trapped-ion computing, simulation and sensing. That is a stated prospect.
Limits
The traps hold few ions, and each paper reports its own metrics, so the heating rate of 2006 and the control demonstrated in 2024 are not comparable. None of them reports a large processor.
What changed across the papers
The three papers cover about two decades of chip-trap work. The first showed that ions can be held in a single plane. The second added many individual control electrodes and showed shuttling, which is how ions are moved between zones in larger architectures. The third swapped the confinement mechanism itself. Each reports a different kind of result: a heating rate, a fabrication and control demonstration, and full quantum control with arbitrary transport. A reader should treat them as stages in a research direction, not as a single measured improvement.
FAQ
What is a surface-electrode trap?
A trap with its electrodes in a plane on a chip, holding the ions above it.
What is a Penning trap?
A trap that uses a magnetic field instead of radio-frequency fields, here 3 T on a chip.
Why avoid radio frequencies?
The 2024 paper lists high voltages, power dissipation and limits on ion transport as scaling challenges.
Could ions be moved around the chip?
The 2010 paper reports shuttling in its traps, and the 2024 paper reports arbitrary transport in the plane.
Is a large trapped-ion chip built?
These papers do not report one.
All field notes