Feature: Interconnects
Interconnects in quantum computers
By Martin Spooner, Engineering Director, Intelliconnect (Europe) W
ith the increasing interest in quantum computing and the
development of large-scale high-qubit machines, there’s a requirement for microwave cables that connect the control and readout lines to the quantum processor. Traditionally, these have been coaxial cables fitted with SMA connectors, which offer limited packaging due to their 8mm hex coupling nut that requires additional space for the installation.
New connectors on the block CryoCoax, a division of Intelliconnect, now offers high-density multiway connectors based on the SMPM interface, which not only allow many more coaxial lines in a given space but also simplify their installation and customisation within a dilution refrigerator. Typical spacing using SMA connectors is limited to approximately 16mm, whereas these high-density connectors are designed with a pitch of 4.75mm. The SMPM interface provides a simple push-to-mate connection, only requiring a hex key to tighten the two fasteners.
reaching temperatures under 20mK at the lowest stage. Each cooling stage is separated by a
bulkhead/heatshield to minimise heat transfer. The cables between these stages connect via feedthrough connectors and must provide good thermalisation. Thorough thermalisation of cables, attenuators and microwave components at the various temperature stages is not only important for reducing the heat load on the dilution refrigerator, but also for reducing thermal noise within the system. Glass hermetic seals provide the
vacuum-tight seal at the top of the DR with hermeticity of 1x10-8
CC He/s at
Eight-way high-density attenuator block and eight-way cable assemblies
Quantum processors operate at
Traditional connections using SMA connectors (visible in the background)
temperatures near absolute zero, which can be achieved using a dilution refrigerator (DR). A typical dilution refrigerator has a vacuum-sealed top plate and several cooling stages below it,
30 December 2021/January 2022
www.electronicsworld.co.uk
Handling the cooling stages Standard non-hermetic feedthrough plates are required between the various cooling stages, and these have machined mounting holes for the connectors.
1Atm. These can be incorporated into custom-designed top plates as well as standard ISO- or KF-style plates. A typical ISO-100 plate can support up to 120 coax lines, depending on connector configuration. Custom plates are capable of supporting many more coax lines.
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