Quantum computing apparatus with interposer and methods of fabrication and operation thereof, quantum computing apparatus comprising tantalum nitride and method of fabrication thereof

The quantum computing apparatus according to any of the preceding claims, wherein the substrate layer is made from sapphire, silicon, BeO, AlN, quartz, and/or any other dielectric material, and/or wherein the patterned layer is made from a superconducting material such as Al, Nb, NbN, NbTiN, tantalum, preferably tantalum nitride.

The quantum computing apparatus according to any of the preceding claims, wherein the patterned layer is formed by atomic layer deposition, evaporation, molecular-beam epitaxy and/or sputtering.

The quantum computing apparatus according to any of the preceding claims, wherein the interposer, preferably the connection element, is made from the same material as used for the substrate layer.

The quantum computing apparatus according to any of the preceding claims, wherein the connection element, comprises a connection substrate layer, or a connection substrate layer and a connection patterned layer adjacent and parallel to the connection substrate layer wherein the connection patterned layer comprises an electrically conductive material:

• preferably wherein the connection substrate layer is made from sapphire, silicon, BeO, AlN, quartz, and/or any other dielectric material, and/or preferably wherein the connection patterned layer is made from a superconducting material such as Al, Nb, NbN, NbTiN, tantalum, preferably tantalum,
• preferably wherein the connection patterned layer is coated with a conductive layer.

The quantum computing apparatus according to any of the preceding claims, wherein

• the qubit comprises a superconducting qubit, a spin qubit, a trapped ion, or a neutral atom;
• and/or wherein the patterned layer further forms a quantum computing circuit, wherein the quantum computing circuit comprises a photonic quantum circuit and/or another chip element, preferably control electronics, readout circuit, amplifiers, filters and/or a transducer.

The quantum computing apparatus of any of the preceding claims, wherein the connection element further comprises a functional element, the functional element being a circuit component which gets input from and/or sends output to the qubit and/or wherein the functional element modifies the input/output signal from the quantum computing circuit component preferably wherein the functional element comprises a low pass filter, an attenuator, a DC-block, an IR filter, a directional coupler, a routing line, a circulator, and/or an amplifier.

The quantum computing apparatus of any of the preceding claims, wherein the connection element has at least one of the following functions:

• microwave drive, flux bias, feedline input/output, pump for the amplifier or circulator, parametric amplifier, circulator, directional coupler or routing lines.

The quantum computing apparatus of any of the preceding claims, wherein routing to and/or from the qubit is at least partly done via the connection element.

The quantum computing apparatus according to any of the preceding claims, wherein the interposer is connected directly to the patterned layer, or wherein the interposer is connected indirectly to the patterned layer, preferably through a via.

The quantum computing apparatus according to any of the preceding claims, wherein the connection element and the layer stack each have a connection surface with a connection profile for mechanically and/or electrically coupling the connection element to the layer stack, preferably wherein the connection surface of the layer stack is an outermost layer of the layer stack, more preferably wherein the connection surface of the layer stack is the patterned layer, preferably wherein the connection profile comprises a coupling structure, preferably a recess, a protrusion, a coupling pin;

• preferably wherein the coupling structure is self-aligning.

The quantum computing apparatus according to any of the preceding claims, further comprising a connectable circuit component, wherein the connection element is an intermediate link between the layer stack, preferably the qubit, and the connectable circuit component:

• preferably wherein the connectable circuit component comprises a connectorized circuit, more preferably a printed circuit board or an array of waveguides.

The quantum computing apparatus according to any of the preceding claims, wherein the interposer comprises an array of connection elements which are substantially parallel to each other and at an angle, preferably substantially orthogonal, to the layer stack and wherein each connection element of the array is connected to the patterned layer, preferably wherein the connection elements are spaced with a particular spacing related to the spacing of the qubits on the horizontal plane.

The quantum computing apparatus of any of the preceding claims, wherein the layer stack comprises multiple patterned layers deposited on one or more substrate layers, each patterned layer comprising a quantum circuit component, preferably a qubit.

The quantum computing apparatus of any of the preceding claims, wherein the layers in the layer stack and/or layers in the connection element are connected through through-silicon via, preferably wherein the layer stack and/or the connection element comprises a through via and/or a blind via.

The quantum computing apparatus of any of the preceding claims, wherein a second interposer is mechanically connected to the layer stack at an opposite end of the layer stack of where the interposer is mechanically connected to the layer stack, preferably wherein the input feedlines of the patterned layer are provided via the interposer, and the output feedlines of the patterned layer are provided via the second interposer.

The quantum computing apparatus of any of the preceding claims, wherein multiple interposers are mechanically and electrically connected to a connection surface of the layer stack, and/or wherein multiple layer stacks are alternated with interposers.

A method of performing a quantum computing operation, using a quantum computing apparatus according to any of the preceding claims.

A quantum computing apparatus, comprising:

• a substrate layer;
• a patterned layer adjacent and parallel to the substrate layer such that the substrate layer and the patterned layer form a layer stack, wherein the patterned layer comprises an electrically conductive material and wherein the layer stack forms at least one quantum computing circuit component, preferably a ground plane, resonator, waveguide and/or qubit capacitor;
• wherein the electrically conductive material comprises tantalum nitride.