Blueprint for a microwave trapped ion quantum computer

Abstract

Design to build a trapped ion quantum computer with modules connected by ion transport and voltage-driven quantum gate technology.

Co-designing a scalable quantum computer with trapped atomic ions

“…Through the use of individual optical addressing of ions 29,30 and pulse-shaping techniques, 31 these errors should not be debilitating for the full control of single crystals ranging from N = 10-100 qubits. In order to scale beyond~50 trapped ion qubits, we can shuttle trapped ions through space in order to couple spatially separated chains of ions, in a multiplexed architecture called the quantum charge-coupled device (QCCD) 23,32,33 and depicted in Figure 2b. The QCCD architecture requires exquisite control of the atomic ion positions during shuttling and may require additional atomic ion species to act as 'refrigerator' ions to quench the excess motion from shuttling operations.…”

High-Fidelity Preservation of Quantum Information During Trapped-Ion Transport

“…Lx,37.10.Ty Ion traps have been a workhorse in demonstrating many proof-of-principle experiments in quantum information processing using small ion samples [1]. A major challenge to transform this ansatz into a powerful quantum computing machine that can handle problems beyond the capabilities of classical super computers remains its scalability [2][3][4][5]. Error correction schemes allow us to fight the ever sooner death of fragile quantum information stored in larger and larger quantum systems, but their economic implementation requires computational building blocks to be executed with sufficient fidelity [6,7].…”

“…Even though, for instance, transverse modes and anharmonic trapping [20] may be employed for conditional quantum logic, a general claim might be that, at some point it is useful to divide a single ion register into subsystems and to exchange quantum information between these subsystems [2][3][4][5]. One might do that by transferring quantum information from ions to photons (and vice versa) and by then exchanging photons between subsystems [4,21].Alternatively, when exchanging quantum information between spatially separated individual registers within an ion trap-based quantum information processor, the transport of ions carrying this information is an attractive approach [2,3,5]. Methods to transport ions in segmented Paul traps have been developed and demonstrated [22][23][24][25], and optimized with respect to the preservation of the motional state during transport [26,27].…”

“…To have the entire error correction sequence be beneficial, the constraints on the individual operations are obviously more stringent. For all correction schemes involving ion transport, the number of transport operations are bigger compared to or much larger than one [2,3,5,29], so the infidelity must, at least, be an order of magnitude smaller than acceptable for the entire sequence.Therefore, in addition to high fidelity local gates, high fidelity transport is required to not cross a desired error threshold when carrying out single-and multiqubit quantum gates.Several experiments have characterized the internal state fidelity F = ψ|ρ|ψ upon transport by measuring the loss of coherence of a prepared superposition state |ψ which dephases into a mixed state ρ during a Ramsey-type measurement. However, the precision reached in these experiments was not yet sufficient to conclude that transport takes place in the fault-tolerant regime required for scaling [22, 24, 26, 27][30].…”

“…Even though, for instance, transverse modes and anharmonic trapping [20] may be employed for conditional quantum logic, a general claim might be that, at some point it is useful to divide a single ion register into subsystems and to exchange quantum information between these subsystems [2][3][4][5]. One might do that by transferring quantum information from ions to photons (and vice versa) and by then exchanging photons between subsystems [4,21].…”