A superconducting device, a superconducting apparatus, a method for manufacturing a superconducting device, and a method for manufacturing a superconducting apparatus

Abstract

A superconducting device (100) comprising at least a first superconducting material layer (102) provided on a substrate (002) and at least one trapping element (200) for reducing quasiparticle density in the first superconducting material layer. The at least one trapping element is embedded within the first superconducting material layer and comprises at least one trapping material (104) and at least one first insulating layer (106a), wherein said first insulating layer is provided between at least a portion of the at least one trapping material and the first superconducting material layer.

Description

[0001] A SUPERCONDUCTING DEVICE, A SUPERCONDUCTING APPARATUS, A METHOD FOR MANUFACTURING A SUPERCONDUCTING DEVICE, AND A METHOD FOR MANUFACTURING A SUPERCONDUCTING APPARATUS

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The invention relates to superconducting devices in general. More specifically, the invention relates to a superconducting device comprising a first superconducting material layer and at least one trapping element embedded in the first superconducting material layer. The invention also relates to a superconducting apparatus comprising such superconducting device comprising at least one embedded trapping element and to a method of manufacturing the superconducting device and the superconducting apparatus.

[0004] BACKGROUND OF THE INVENTION

[0005] Superconducting devices have many potential uses including e.g. quantum devices, sensor devices, and in connection with cryogenic applications. The performance of many of these superconducting devices is hindered by the presence of quasiparticles in the device.

[0006] Quasiparticles result from the breaking apart of Cooper pairs, which are present in superconductors, when one of the electrons in the pair is excited to a higher energy level.

[0007] At low temperatures, i.e. well below the critical temperature of superconducting materials, only Cooper pairs should be found in the superconducting materials. However, it has been demonstrated that non-equilibrium quasiparticles, i.e. unpaired electrons or quasiparticle excitations (also simply termed quasiparticles herein), are found in superconducting materials at temperatures well below their critical temperature. The reasons for such excitations are currently at least partially unknown, although there have been some indications that environmental radioactive materials and cosmic-ray bursts may generate the quasiparticles. Thus, the generation of quasiparticles may be difficult to avoid in devices in any practical solutions, and it would be advantageous to find solutions for reducing the density or mitigation of quasiparticles that have been formed in superconducting devices.

[0008] The non-equilibrium quasiparticles negatively affect the functioning of superconducting devices. For example, the quasiparticle reduces the quality factor of superconducting resonators. In the case of superconducting devices being qubits and comprising a Josephson junction, for instance, quasiparticles can tunnel to the Josephson Junction and cause qubit energy decay and decoherence, which limits the lifetime and stability of the qubits. Furthermore, it is known that one side effect of the Single Flux Quantum (SFQ) pulses, used for scaling up the qubits, is the generation of quasiparticles that can then limit the gate fidelities. As further disadvantages related to qubits, it is known that the presence of quasiparticles affect energy levels of qubits, leading to shifts of qubit frequencies and that quasiparticles may limit the relaxation time of superconducting qubits. In superconducting qubits, it has been firmly established both theoretically and experimentally that quasiparticle tunneling causes qubit energy decay and dephasing. The mitigation of effects of quasiparticles on qubits may provide more stable and long-lived qubits, which can facilitate the further development of quantum computing devices.

[0009] Another example of superconducting devices where quasiparticles may cause problems are Josephson-junction based sensor devices, where measurements dependent on current flowing through a Josephson junction. Here, tunnelling quasiparticles may cause these devices to not function as desired.

[0010] There have been attempts to reduce the number of quasiparticles in superconducting devices, by using methods or structures known as quasiparticle traps. It is known that vortices may be used for such purposes, but this requires cooling in a magnetic field, which makes the method unsuitable for many devices, such as 2D transmons. Furthermore, vortices are also difficult to control and a large number of them could negatively influence the performance of a superconducting device.

[0011] Other prior art quasiparticle traps may comprise a normal-conductivity metal layer that is coupled to the superconducting device, such that they are separated by an insulator layer to provide a superconductor - insulator - normal-conductivity metal (SIN) junction. These traps may evacuate quasiparticles from a superconducting material of a superconducting device by quasiparticles tunneling through to the normal-conductivity metal layer, and upon relaxation of the quasiparticle in the normal-conductivity metal layer below the superconducting gap, the density of quasiparticles present in the superconducting device is thus reduced. This results in a more stable and long-lived superconducting device. Such prior art quasiparticles traps are known from e.g. A. Hosseinkhani, R.-P. Riwar, R. J. Shoelkopf, L. I. Glazman, G. Catelani, “Optimal configurations for normal-metal traps in transmon qubits,” Phys. Rev. App. 8, 064028, 2017, A. Hosseinkhani and G. Catelani, “proximity effect in normal-metal quasiparticle traps”, Phys. Rev. B 97, 054513 (2018), and. R.-P. Riwar, A. Hosseinkhani, L. D. Burkhart, Y. Y. Gao, R. J. Schoelkopf, L. I. Glazman, G. Catelani, Phys. Rev. B 94, 104516 (2016).

[0012] However, it is known that quasiparticle back tunneling is a problem with the abovedescribed SIN structure of normal-conductivity metal traps. In such back tunneling, quasiparticles with energies above the superconducting gap of the superconducting material can escape from the normal-conductivity metal trap and tunnel back into the superconducting material. The rate of this harmful process is significantly enhanced at energies very close and above the superconducting gap of the superconducting material due to the divergent behavior of the density of states in Bardeen-Cooper-Schrieffer (BCS) superconductors, where the DOS becomes infinite. It has been demonstrated for a structure in which the superconducting material is Aluminum and the normal-metal trap is Copper, that the effective quasiparticle trapping rate is about two orders of magnitude smaller than the rate at which quasiparticles tunnel into the normal-conductivity metal layer, due to the back tunneling.

[0013] Furthermore, state of the art trapping structures, usually consisting of layers of normal conductivity metals, implemented onto superconducting devices actually introduce spurious dissipation, such as ohmic losses, for the superconducting circuits the superconducting devices are designed to protect from excess quasiparticles. Such ohmic losses arising from trapping structures in qubits are shown for example in R.-P. Riwar, L. I. Glazman, and G. Catelani, Phys. Rev. B 98, 024502 (2018).

[0014] It would thus be beneficial to discover a more efficient way to reduce the density of quasiparticles in superconducting devices without having spurious dissipation effect in the superconducting device, especially one that could be utilized with e.g. 2D transmons.

[0015] SUMMARY OF THE INVENTION

[0016] An object of the invention is to alleviate at least some of the problems of the prior art. In accordance with one aspect of the present invention a superconducting device is provided, the superconducting device comprising at least a first superconducting material layer provided on a substrate and at least one trapping element for reducing quasiparticle density in the at least first superconducting material layer. The at least one trapping element is embedded within the first superconducting material layer and comprises at least one trapping material, wherein the trapping element additionally comprises at least one first insulating layer, further wherein said first insulating layer is provided between at least a portion of the at least one trapping material and the first superconducting material layer.

[0017] The present invention may provide an improved superconducting device having a reduced density of quasiparticles compared to a superconducting device of the prior art and / or a superconducting device comprising a trapping structure according to the prior art. The presence of at least one insulating layer between at least a portion of the at least one trapping material and the first superconducting material enables to reduce the rate of quasiparticle tunneling back into the first superconducting material layer and further to reduce the motion of the quasiparticles tunneling back to the first superconducting material layer. Furthermore, the presence of the insulating layer increases the time a quasiparticle spends in the trapping material and therefore increases the probability of the quasiparticles to become trapped in the trapping material.

[0018] Embedding the trapping element according to the invention within a superconducting material layer of the superconducting device enables to reduce the spurious dissipation effect, such as ohmic losses, observed in superconducting devices comprising trapping elements where the trapping elements are actually provided in contact with the superconducting device structure but outside of the superconducting material layers of the superconducting device structure, in particular the trapping element being provided above or below the superconducting material layers of the superconducting device structure.

[0019] The trapping material may comprise a normal-conductivity metal material and / or a superconducting material. A superconducting material used in the trapping material may comprise a superconducting energy gap that is lower than a superconducting energy gap of the first superconducting material layer.

[0020] The at least first insulating layer may be a single continuous insulating layer or it may be formed from a plurality of discontinuous insulating layer portions.

[0021] The first insulating layer may be arranged to cover at least partially the trapping material’s surface area, in particular at least 20%, more in particular more than 50%, even more in particular between 60% and 80% of the trapping material’s surface area. The surface area of the trapping material relates to the surface of the trapping material being in contact with the first superconducting material layer, thus relating to the interface or interface area between the trapping material and the first superconducting material layer.

[0022] A resistance of the first insulating layer of the trapping element may be configured to reduce or essentially prevent tunneling back of quasiparticles from the trapping material to the first superconducting material layer via the first insulating layer. The resistance may be at least above 100 Q / pm2, preferably above 500 Q / pm2. Such resistance value results in a high potential barrier of the insulating layer at the first-type interface, resulting in a decrease and / or prevention of tunneling back of the quasiparticles present in the trapping element to the first superconducting material layer.

[0023] While quasiparticles located in the trapping element can tunnel back to the first superconducting material layer, as it happens in prior art trapping structure, the presence of the at least one insulating layer at an interface between the trapping material and the first superconducting material layer enables to reduce the amount of quasiparticles susceptible to tunnel back from the trapping element to the first superconducting material layer at that interface. Thus, the trapping element according to the invention enables to reduce the amount of quasiparticles tunneling back from the trapping element to the first superconducting material layer, improving the superconducting device compared to superconducting devices comprising a prior art trapping element or structure.

[0024] At a first-type interface between the trapping material and the first superconducting material layer, a first insulating layer is present. A second-type interface between the trapping material and the first superconducting material layer is an interface where no first insulating layer is present, and the trapping material may be directly or indirectly coupled to the first superconducting material layer such that quasiparticles are able to tunnel from the first superconducting material layer to the trapping material. As a result, a resistance at the first- type interface between the trapping material and the first superconducting material layer is higher than a resistance at a second-type interface between the trapping material and the first superconducting material layer.

[0025] With the trapping element of the present invention, being embedded in the superconducting material layer, quasiparticles may thus readily tunnel into the trapping material via a second- type of interface, while they are essentially prevented or hindered from tunnelling from the trapping material layer to the first superconducting material layer to the trapping material via a first-type of interface. In particular, the quasiparticles can only tunnel from the first superconducting material layer to the trapping material via the second-type interface. Furthermore, the tunneling back of the quasiparticles from the trapping element is also hindered at the first-type interface where the first insulating layer is provided. Providing such first and second type interfaces of a trapping element with a superconducting material may thus enable reducing the tunneling back of quasiparticles present in the trapping material to the first superconducting material layer. Thus, overall, the tunneling back of quasiparticles is reduced in the superconducting material layer, which results in a reduced density of quasiparticles in the superconducting device overall.

[0026] The relationship between a first-type interface and second-type interface, in terms of surface area, resistance, and / or thickness of an insulating layer or other type of barrier / tunneling layer, if present, between the trapping material layer and first superconducting material layer may affect functioning of the trapping element. Tailoring of such relationship may be utilized to obtain desired qualities for the functioning of the trapping element.

[0027] In one embodiment, the trapping material may have a shape comprising at least a first surface and a second surface, wherein the at least first insulating layer is provided on said first surface of the trapping material and / or on the second surface of the trapping material. The first surface and / or second surface may be surfaces of the trapping material with larger surface areas than remaining surfaces of the trapping material.

[0028] The trapping material may have a shape comprising one or more surface(s), wherein the at least first insulating layer is provided at least partially on at least one or more surface(s).

[0029] A superconducting device may additionally comprise a second superconducting material layer coupled to at least a portion of the first superconducting material layer, wherein the second superconducting material layer is configured to provide a superconducting energy gap that is lower than a superconducting energy gap of the first superconducting material layer.

[0030] A second superconducting material layer may be coupled to a first surface of the first superconducting material layer or to a second surface of the first superconducting material layer.

[0031] A superconducting device may comprise, in addition to a second superconducting material layer, a third superconducting material layer coupled to at least a portion of the first superconducting material layer, wherein the third superconducting material layer comprises a superconducting energy gap that is lower than a superconducting energy gap of the first superconducting material layer. Here, a second superconducting material layer may be coupled to a first surface of the first superconducting material layer and the third superconducting material layer may be coupled to a second surface of the first superconducting material layer.

[0032] In connection with either or both of a second or third superconducting material layer, a further layer may be provided between the second and / or third superconducting material layer and the first superconducting material layer. The further layer may be a further insulating layer. The resistance of said further insulating layer may be at least above 100 Q / pm2, preferably above 500 Q / pm2.

[0033] The second and / or third superconducting material layer may be configured to further reduce a density of quasiparticles in the first superconducting material layer, by enabling tunneling of quasiparticles into the second and / or third superconducting material layer from the first superconducting material layer, while at least a portion of said tunneled quasiparticles may be prevented from tunneling back into the first superconducting material layer due to the lower superconducting energy band gap of the second and / or third superconducting material layer. If a second and / or third superconducting material layer is present, one or both of them may be a discontinuous material layer. The discontinuity may be provided at least in a direction that is essentially parallel to a longitudinal axis of the first superconducting material layer. The discontinuity may essentially prevent quasiparticles present in the second and / or third superconducting material layer from traveling in the second and / or third superconducting material layer essentially parallel to a longitudinal axis of the first superconducting material layer along a direction essentially parallel to the longitudinal axis of the first superconducting material layer. This may be advantageous when a Josephson junction is provided adjacent to the superconducting material layers, as the quasiparticles may be prevented from moving towards / closer to the Josephson junction.

[0034] The first superconducting material layer may comprise one or more regions where the superconducting energy bandgap is lower than the superconducting energy bandgap of the rest of the superconducting material layer. The one or more region(s) is (are) located in the proximity of the second-type interface between a surface of the at least one trapping element and the superconducting material layer, said second-type interface comprising a lower resistance than the first-type interface. In particular, the one or more region(s) is (are) located adjacent to the second-type interface between the at least one trapping element and the superconducting material layer, more in particular directly adjacent, the second- type interface being the interface not having the at least first insulating layer.

[0035] The interface between the one or more regions of the first superconducting material with a lower superconducting bandgap than the superconducting bandgap of the first superconducting material and the at least one trapping element may comprise a resistance lower than the resistance of the interface between the at least first insulating layer of the trapping element and the first superconducting material layer.

[0036] The one or more regions of the first superconducting material layer with a lower superconducting bandgap compared to the rest of the first superconducting material layer may be configured to localize the quasiparticles within the one or more region(s) of the first superconducting material layer, in particular the quasiparticles of the trapping material which tunnel back to the first superconducting material layer. Thus, even such quasiparticles that are able to tunnel back to the first superconducting material layer from the trapping element may be prevented from further travel inside the first superconducting material layer, due to them being trapped / localized at the region(s) of the first superconducting material layer with a lower superconducting bandgap compared to the rest of the first superconducting material layer. As compared to prior art superconducting devices with quasiparticle traps, the present invention may provide a way of trapping quasiparticles by reducing the quasiparticle density and / or their dynamics in the first superconducting material layer of the superconducting device which in turn results in less spurious dissipation, e.g ohmic losses, in the superconducting device according to the invention. The prior art normal conductivity metal layer coupled to the superconducting material layer may result in more spurious dissipation than the present invention, as they introduce ohmic losses within the superconducting device, compared to the case where one or more trapping elements are embedded in the first superconducting material layer. Indeed, the one or more trapping elements are shunted and shielded by the superconducting material, which prevents the introduction of eddy currents within the device. Furthermore, shielding of the trapping elements by the superconducting material reduces eddy currents coupling to the trapping elements from free space. The superconducting material shunt diminishes any voltage drop across the trapping element and hence protects the superconducting electronics from direct ohmic losses. The spurious dissipation reduction obtained with the trapping structure of the present invention may be even more advantageous with e.g. qubit devices, where the qubit quality required is higher and thus spurious dissipation may be even more important.

[0037] A superconducting device may comprise a plurality of trapping elements, each trapping element comprising at least one trapping material and at least a first insulating layer, wherein each trapping element is embedded within the first superconducting material layer, such that the first superconducting material layer is in contact with the first insulating layers of each of the plurality of trapping elements. The plurality of trapping elements may be distributed within the first superconducting material layer such that each of the plurality of trapping elements are separated from each other. As a result, the trapping elements are shunted and shielded by the first superconducting material layer, instead of having a large slab of trapping material within the superconducting device not being embedded in the superconducting material layer as trapping structure as in the prior art. The shielding of the trapping elements by the superconducting material reduces eddy current coupling to the trapping material, especially when normal conductivity metal is used as trapping material, from free space. The superconducting material shunt diminishes any voltage drop across the trap and hence protects the superconducting electronics from such direct ohmic losses.

[0038] A superconducting apparatus may comprise a plurality of superconducting devices according to the invention, wherein the separate superconducting devices are coupled to each other via a Josephson junction. At least one Josephson junction of a superconducting apparatus may be formed at at least one edge of a first superconducting layer of a superconducting device, in a direction substantially parallel to a longitudinal axis of the first superconducting layer.

[0039] A method of manufacturing a superconducting device may comprise providing at least a first superconducting material layer, providing at least one trapping element comprising a trapping material, wherein the trapping element is provided as being embedded in the first superconducting material layer, wherein the providing at least one trapping element comprises providing at least a first insulating layer positioned between at least a portion of the at least one trapping material and the first superconducting material layer.

[0040] The method can also comprise providing a plurality of trapping elements embedded in the first superconductor material layer.

[0041] A method of manufacturing a superconducting apparatus may comprise providing a plurality of superconducting devices according to the invention, wherein the separate superconducting devices are coupled to each other via a Josephson junction. Such a method may comprise manufacturing a plurality of superconducting devices, the method additionally comprising providing at least one Josephson junction to couple at least two adjacent superconducting devices to each other.

[0042] The exemplary embodiments presented in this text are not to be interpreted to pose limitations to the applicability of the appended claims. The verb "to comprise" is used in this text as an open limitation that does not exclude the existence of also unrecited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated.

[0043] The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific example embodiments when read in connection with the accompanying drawings.

[0044] BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Next the invention will be described in greater detail with reference to exemplary embodiments in accordance with the accompanying drawings, in which:

[0046] Figure 1 shows a cross-sectional view of at least a portion of an exemplary superconducting device according to the invention, Figure 2 shows a cross-sectional view of a second example of a superconducting device according to the invention,

[0047] Figure 3A shows a cross-sectional view of another example of a superconducting device according to the invention,

[0048] Figure 3B shows a cross-sectional view of another example of a superconducting device according to the invention,

[0049] Figure 4A shows a cross-sectional view of another example of a superconducting device according to the invention,

[0050] Figure 4B shows a sideview of the superconducting device of Fig. 4A along an AA axis cut,

[0051] Figure 5 shows a cross-sectional view of another example of a superconducting device according to the invention,

[0052] Figure 6 presents a cross-sectional view of another example of a superconducting device according to the invention,

[0053] Figure 7 shows a cross-sectional view of another example of a superconducting device according to the invention,

[0054] Figure 8 shows an example of a superconducting apparatus according to the invention, and

[0055] Figure 9 presents a flow chart of an exemplary method of manufacturing a superconducting device according to the invention.

[0056] DETAILED DESCRIPTION

[0057] All figures depicted should be considered as schematic examples and e.g. the proportions of different layers or other components are not shown to scale. The devices shown in the figures are cross-sectional views of devices, unless otherwise stated.

[0058] Fig. 1 shows a cross-sectional view of one example of at least a portion of an exemplary superconducting device 100. The device 100 comprises a substrate 002 and at least a first superconducting material layer 102. The at least first superconducting material layer 102 is provided on the substrate 002. The substrate 002 can be made of silicon, any silicon-based material or sapphire-based substrate. A material comprised in the first superconducting material layer 102 may be aluminum, niobium, tantalum, niobium-titanium, titanium-nitride, niobium nitride or any alloy of the previous materials, to name a few examples.

[0059] The superconducting device 100 may be a device comprising at least a first superconducting material layer 102 and at least one Josephson junction or the superconducting device 100 may be configured to be coupled to at least one Josephson junction. The superconducting device 100 may be e.g. a resonator, a sensor device, a cryogenic device, or a quantum device.

[0060] The superconducting device 100 may in one example be a qubit device or a portion of a qubit device. The first superconducting material layer 102 may in one embodiment be a superconducting lead of a qubit device.

[0061] The first superconducting material layer 102 may generally be a material layer that has a shape with at least a length that is larger than a thickness. A dimension of the first superconducting material layer 102 may then be larger in at least a longitudinal axis direction A of the first superconducting material layer 102 than in a transverse axis direction At.

[0062] The superconducting device 100 additionally comprises at least one trapping element 200, where the trapping element comprises at least one trapping material 104 and at least a first tunneling layer 106.

[0063] The trapping material 104 may comprise a normal-conductivity metal material, such as gold, palladium, copper, or silver, with the normal-conductivity metal material being a single metal or a combination of metals, like for example AuPd. The trapping material 104 may additionally or alternatively comprise a superconducting material that has a superconducting energy gap that is lower than a superconducting energy gap of the first superconducting material layer 102. The trapping material 104 may be a combination of one or more normal-conductivity metal materials and one or more superconducting materials that have a superconducting energy gap that is lower than a superconducting energy gap of the first superconducting material layer 102. The trapping material 104 may e.g. itself comprise a layer structure, comprising a normal conductivity layer / core, surrounded by a superconducting material layer that has a superconducting energy gap that is lower than a superconducting energy gap of the first superconducting material layer 102.

[0064] The trapping material 104 may be an entity comprising a trapping material, such that the trapping material 104 is not the same material as the first superconducting material layer 102. The trapping material 104 may be provided as a trapping material layer or as a trapping material portion of the superconducting device 100.

[0065] The first insulating layer 106 may comprise an oxide material or some other insulating material. For example, the first insulating layer 106 could be a native oxide or an oxide layer being deposited or a combination of oxide layers. A thickness t of the first insulating layer 106 may be comparable to oxide layers typically used in junctions. The thickness of the insulating layer 106 may be e.g. about 1 nm or above.

[0066] In general, the trapping element 200 is smaller in dimensions than the first superconducting material layer 102 and the trapping element 200 is fully embedded in the first superconducting material layer 102. In some embodiments, the trapping element 200 may be embedded in the first superconducting material layer 102 such that a portion of the surface area of the trapping element 200 is not buried within the first superconducting material layer 102, i.e. the trapping element 200 may be provided at an edge of the first superconducting material layer 102. In that case, for example, a surface of the trapping element 104 or a surface of the at least one insulating layer 106 can be adjacent to the surface 112, 114 of the superconducting material layer 102.

[0067] The first insulating layer 106 is provided between the first superconducting material layer 102 and the trapping material 104, such that the first insulating layer 106 covers at least a portion of the surface area of the trapping material 104. In that case, another portion of the surface area of the trapping material 104 may then not be in contact with the first insulating layer 106. This results in a first-type of interface between the trapping material 104 and the first superconducting material layer 102 comprising an insulating layer 106 and a second- type of interface not comprising any insulating layer 106, where the trapping material 104 may be direct contact with the first superconducting material layer 102.

[0068] In the example of superconducting device shown in Fig. 1 , the trapping material 104 is provided as a trapping material layer. The trapping element 200 may provide a first-type of interface 110 between the trapping material layer 104 and the first superconducting material layer 102 where the first insulating layer 106 is present, and a second-type of interface 108a, 108b, 108c between the trapping material layer 104 and the first superconducting material layer 102 where no first insulating layer 106 is present.

[0069] The trapping element 200 can also have a different number of first-type and second-type interfaces than the one described previously. For example, it can also have more first-type interfaces than second-type interfaces, or vice versa. Due to the presence of the insulating layer 106 at the interface between the trapping material 104 and the first semiconductor material layer 102, the first-type interface 110 may provide a higher resistance between the trapping material 104 and the first superconducting material layer 102 compared to the second type interface(s) 108a, 108b, 108c. The second- type interfaces may be configured, via selected resistances, to enable or allow tunneling of quasiparticles from the first superconducting material layer 102 into the trapping material layer 104. The first-type interfaces 110 may be configured to prevent tunneling of quasiparticles from the first superconducting material layer 102 to the trapping material layer 104 by providing high resistance due to the presence of the first insulating layer 106 at this interface. At the same time, the first-type interface 110 will also prevent or reduce the back tunneling of quasiparticles from the trapping material layer 104 into the first superconducting material layer 102 by providing high resistance due to the presence of the first insulating layer 106 at this interface 110. Thus, the first-type interface 110 may be configured to reduce the motion of quasiparticles between the trapping material 104 and the first superconducting material layer 102 at this interface 110 compared to the case where a trapping element 200 embedded in the superconducting material layer 102 does not comprise an insulating layer 106 at an interface 110 between the trapping material 104 and the superconducting material layer 102. In a variant, the first-type interface 110 may be configured to prevent the motion of quasiparticles between the trapping material 104 and the first superconducting material layer 102 at this interface 110. This is due to the high potential barrier provided at the interface 110 by the insulating layer 106.

[0070] For example, the resistance at the first-type interface 110 may be one order of magnitude higher than the resistance at the second-type interface 108.

[0071] Basically, the presence of the insulating layer 106 at the first-type interface reduces and / or prevents the tunneling of quasiparticles between the first superconducting material layer 102 and the trapping material 104 in whatever direction of motion of the quasiparticles, so that the quasiparticles motion between the superconducting material layer 102 and the trapping element 200 is mainly taking place via the second-type interfaces. Furthermore, the presence of the insulating layer 106 increases the time a quasiparticle spends in the trapping material 104 and therefore increases the probability of the quasiparticles to become trapped in the trapping material 104 of the trapping element 200.

[0072] The first insulating layer 106 may be tuned to provide a selected resistance at the first-type interface(s) 110. This can be achieved by providing a selected thickness or a selected material, for the first insulating layer 106. A first insulating layer 106 or portions thereof and associated resistance(s) may be selected based on a surface area of the trapping element or trapping material or surface area in contact with the first superconducting material layer 102.

[0073] A shape and / or size of any of the components of the superconducting device 100, such as first superconducting material layer 102, trapping material 104, and / or insulating material layer 106 may vary. Some examples of different shapes of trapping elements, relating specifically to shapes of trapping material, in general will be given further below.

[0074] In the example of Fig. 1 , the trapping material 104 relates to a trapping material layer 104 which comprises a hexahedral shape with a first surface, in this example corresponding to that shown in connection with the first-type interface 110, and a second surface, in this example corresponding to that shown in connection with a second-type interface 108c. The first surface and second surface of the trapping material layer 104 may be surfaces that have a larger surface area than other surfaces of the trapping material layer 104. The first and second surfaces of the trapping material layer 104 may be essentially codirectional with a first surface 112 of the first superconducting layer 102 and second surface 114 of the first superconducting material layer 102. In other embodiments, the first and second surfaces of the trapping material layer 104 (being surfaces with larger surface area than other surfaces of the trapping material layer 104) may be essentially perpendicular to a first surface 112 of the first superconducting layer 102 and second surface 114 of the first superconducting material layer 102.

[0075] The first insulating layer 106 may be provided at one or both of the first and / or second surfaces. In the example of Fig. 1 , the first insulating layer 106 is only provided at the first surface 110 of the trapping material 104.

[0076] At the second type interface(s) 108a, 108b, 108c, localization areas 116a, 116b, 116c may be formed. Localization areas are highlighted in the figures by encircling areas with dashed lines. The localization areas 116a, 116b, 116c may be areas of the first superconducting material layer 102 that have a reduced superconducting energy gap Ar as compared to the superconducting energy gap i that is exhibited by other portions of the first superconducting material layer 102.

[0077] The reduced superconducting energy gap of the first superconducting material at the one or more localization areas 116a, 116b, 116c may be provided due to the proximity effect, which arises when a superconducting material is provided close to a trapping material. The proximity effect results in a reduction of the superconducting energy gap Ai of the first superconducting material layer 102 in the localization areas 116a, 116b, 116c compared to the rest of the superconducting material layer 102. This reduction in gap Ar may take place within a portion of the first superconducting material layer 102, being close to the interface with the trapping material 104. Thus, the superconducting energy gap Ai of the first superconducting material layer 102 may vary with the material, with the energy gap being suppressed / reduced to a varying degree.

[0078] The proximity effect also leads to a broadening of density of states of the first superconducting material 102. The proximity effect is usually considered as a detrimental phenomenon, but in connection with the present invention, may give a beneficial effect. The proximity effect is described for example in A. Hosseinkhani and G. Catelani, Phys. Rev. B 97, 054513 (2018).

[0079] Through the llsadel theory of superconductivity, the coupling strength of an interface between a superconducting material layer and a normal conductivity metal material layer may be characterized via the dimensionless quantity TA, where A is the superconducting energy gap of the superconducting material and where:

[0080] T = 2e2vsdR^tA. (1 )

[0081] Here vsis the density of states at the Fermi level of the first superconducting material layer, d is the thickness of the first superconducting material layer and R™4 is the interface resistance between the first superconducting material layer and the trapping material layer times an area of the interface.

[0082] The density of states n(e) and the reduced superconducting gap Alzmay be found by numerical self-consistent solution of the llsadel equation. However, if the coupling strength may be considered as weak, i.e. TA» 1, approximate solutions from the Usadel theory can be formulated as: and where Ai is the superconducting energy gap or bandgap of the material of the first superconducting material layer 102 in the absence of the proximity effect.

[0083] We can also be in a strong coupling regime; in that case, the behavior of the system can be described by numerical solution of the Usadel equation. Equations (2) and (3) then show a broadening of density of states in the first superconducting material and the lowering of the superconducting energy gap Ai of the first superconducting material layer 102 that follow from the proximity effect and weak coupling between the first superconducting material layer 102 and the trapping material layer 104.

[0084] The form of the modified density of states n(e) then follows the well-known phenomenological Dynes form. It may be noted that the density of states approaches the BCS relation once the interface resistance becomes very large so that the proximity effect becomes negligible,

[0085] T — > oo,

[0086] Thus, the presence of an insulating layer 106 between the trapping material 104 and the first superconducting material 102 reduces the proximity effect.

[0087] The above approximate solutions are valid for structures comprising a normal-conductivity metal material used as the trapping material 104. Similar considerations, however, regarding e.g. the proximity effect are valid also considering trapping materials 104 comprising a superconducting material having a superconducting energy bandgap that is lower than a bandgap of the first superconducting material layer 102.

[0088] Through the broadening of density of states and the lower superconducting energy gap at the localization area(s) 116a, 116b, 116c of the first superconducting material layer 102, any quasiparticles that have tunneled to the trapping material 104 from the first superconducting material layer 102 but have not relaxed in the trapping material 104 and are able to tunnel back into the first superconducting material layer 102 will do so via the second type interface and may still be trapped or localized at the localization area(s) 116a, 116b, 116c. This is due to available energy states provided around the superconducting gap Alzat energies that are lower than the superconducting energy gap Ai of the rest of the first superconducting material layer 102, with transitions from these lower energy states back into the first superconducting material layer 102 then being unallowable.

[0089] As a result, the motion of quasiparticles within the first superconducting material layer 102 will be reduced due to the localization of quasiparticles within the localization areas 116a, 116b, 116c of the first superconducting material layer 102. Thus, the amount of quasiparticles travelling within the first superconducting material layer 102, and which could thus move closer to a Josephson junction, is reduced compared to a superconducting device of the prior art or comprising a trapping element of the prior art. In some embodiments, some or all of the second type interface(s) 108a, 108b, 108c may not be direct interfaces between the first superconducting material layer 102 and the trapping material 104, but a further layer may be provided at the interface. This further layer may be a tunneling layer, that provides a resistance that is smaller than that of the first insulating layer 106. A tunneling layer may e.g. be (significantly) thinner than the first insulating layer 106.

[0090] In particular, a tunneling layer may be a second insulating layer, for example a native oxide layer. A tunneling layer may comprise properties (in terms of e.g. thickness) as insulation layers known to be generally provided in connection with tunnel junctions. A second insulating layer may comprise a thickness that is lower than the first insulating layer.

[0091] The tunneling layer, if present, at the second type interface 108 may be configured so that the motion, namely the tunneling of the quasiparticles from the first superconducting material layer 102 to the trapping element 200 or vice versa, is still possible at the second- type interface 108, however somehow reduced compared to the case when no tunneling layer is present at the second-type interface 108.

[0092] Figure 2 shows an example of a superconducting device 100 that is otherwise similar to the superconducting device 100 shown in Figure 1 , but instead of the first insulating layer 106 being arranged only at a first surface area 110a of the trapping material 104, the first insulating layer 106a, 106b is provided on the first surface area 110a and also on a second surface area 110b of the trapping material 104. Thus, the trapping element 200 comprises a first insulating layer 106 provided on more than one surface of the trapping material 104. Again, here in Figure 2 like for Figure 1 , the trapping material 104 is configured as a trapping material layer 104, and thus comprises four surfaces. In Figure 2, the first surface 110a and the second surface 110b are surfaces of the trapping material layer with larger surface areas than remaining surfaces of the trapping material 104.

[0093] The first insulating layer 106a, 106b may be configured to cover partially the surface areas 110a, 110b of the trapping material 104.

[0094] In the example of Fig. 2, the first insulating layer 106a, 106b is associated with first-type interfaces 110a, 110b through which the tunneling back of quasiparticles from the trapping material layer 104 to the first superconducting material layer 102 may be reduced or prevented.

[0095] In the example of Fig. 2, the trapping material layer 104 may comprise a normal conductivity metal material and / or a superconducting material with an energy bandgap lower than the energy bandgap of the first superconducting material layer 102 and the localization areas 116a, 116b may be formed adjacent to the second-type interfaces 108a and 108b, within the first superconducting material layer 102. In the example of Fig. 2, only two localization areas 116a, 116b are present within the first superconducting material layer 102, due to the presence of the insulating layer 106 on two surface areas 110a, 110b of the trapping material 104.

[0096] In a variant, the first insulating layers 106a, 106b may be provided at a surface(s) of the trapping material 104, which are not surfaces that have larger surface area, but the surfaces which have the lower surface area of all the surfaces of the trapping material 104.

[0097] Figures 3A and 3B show embodiments of superconducting devices 100 comprising a trapping element 200 with a spherically shaped trapping material 104. In the example of Fig. 3A, the first insulating layer 106 is a continuous material layer covering a portion of the surface area of the trapping material 104 that provides a first-type interface 110 between the trapping material 104 and the first superconducting material layer 102. A second-type interface 108 may be provided at a remaining surface area of the trapping material 104 that is in contact with the first superconducting material layer 102 as no first insulating layer 106 is provided.

[0098] A localization area 116 is present within the first superconducting material layer 102, being located in proximity to the second-type interface 108, so that the localization area 116 is adjacent and in contact with the trapping material 104. At the second-type interface 108, a further layer, such as a barrier layer, a thin tunneling layer (thin as compared to the first insulating layer 106) or low resistance providing layer, may be provided between the first superconducting material layer 102 and the trapping material 104, and thus between the localization area 116 and the trapping material 104.

[0099] In the example of Fig. 3B, the first insulating layer 106a, 106b is discontinuous over the surface area of the trapping material 104 and is provided to cover two portions of the surface area of the trapping material 104. First-type interfaces 110a, 110b are then provided accordingly, as well as second-type interfaces 108a, 108b. Two localization areas 116a, 116b are present within the first superconducting material layer 102, each being located in proximity to one of the second-type interface 108a, 108b so that the localization areas 116a, 116b are in contact with the trapping material 104.

[0100] Figures 4A and 4B present one more example of a superconducting device 100 according to the invention. The device comprises at least one trapping element 200, here comprising an elongated rectangular shape from which extend a plurality of further elongated rectangular shapes.

[0101] Figure 4A shows a cross-sectional view of the superconducting device 100, while Fig. 4B shows a further sliced view along the section AA of Figure 4A. The trapping element 200 comprises a trapping material 104 and a first insulating layer 106 arranged to cover at least a portion of the surface of the trapping material 104. In this embodiment, the trapping material 104 may be provided as a layer and be called a trapping material layer 104.

[0102] Figure 5 gives an example of a superconducting device 100 wherein a plurality of trapping elements 200 are embedded in the first superconducting material layer 102. In Fig. 5, each trapping element 200 of the plurality of trapping elements is the same. The five trapping elements 200 shown on Fig. 5 are separated from each other and are distinct trapping elements 200. In the example shown in Fig. 5, each trapping element 200 comprises a trapping material 104 and a first insulating layer 106 provided on two surfaces of the trapping material 104 of each of the trapping element 200. In that case, each trapping element 200 of the plurality of trapping elements is associated with two localization areas 116a, 116b within the first superconducting material 102 and in close proximity to the second-type interface between the trapping material 104 and the first superconducting material layer 102.

[0103] The trapping elements 200 of the plurality of trapping elements may all be similar or they may be different, e.g. in terms of shape, size, materials, and / or type and number of first insulating layer 106 being present at the surface of the trapping element. For example, the thickness and / or the material of the first insulating layer 106 and / or surface area of trapping material layer 104 covered by the first insulating layer 106 can be the same or different. As a result, each trapping element 200 might have the same of different localization areas 116a, 116b, e.g. in terms of shape, size and number, in the first superconducting material layer associated to each trapping element 200.

[0104] A plurality of trapping elements may be evenly or unevenly distributed within the first superconducting material layer 102. A plurality of trapping elements may reduce more effectively the density of quasiparticles in the first superconducting material layer 102 compared to having only one trapping element 200 embedded in the superconducting material layer 102.

[0105] Figure 6 shows an example of a superconducting device 300 according to the invention. The superconducting device 300 corresponds to the superconducting device 100 shown in Fig. 2 further comprising an additional second superconducting material layer 120 and a third superconducting material layer 122, both layers being coupled to at least a portion of the first superconducting material layer 102.

[0106] The additional second superconducting material layer 120 is provided on at least a portion of the first superconducting material layer 102 via the first surface 112 of the first superconducting material layer 102. The second superconducting material layer 120 could also be provided at the second surface 114 of the first superconducting material layer 102 (if only one additional superconducting material layer is provided). The second superconducting material layer 120 may comprise a superconducting material that has a superconducting energy gap A2 that is lower than a superconducting energy gap A1 of the superconducting material of the first superconducting material layer 102.

[0107] The third superconducting material layer 122 is provided on the second surface 114 of the first superconducting material layer 102. The third superconducting material layer 122 may comprise a superconducting material that has a superconducting energy gap A3 that is lower than a superconducting energy gap A1 of the superconducting material of the first superconducting material layer 102.

[0108] A superconducting energy gap of a second superconducting material layer 120 and / or third superconducting material layer 122 may be provided through a second superconducting material layer 120 and / or third superconducting material layer 122 that comprises a different superconducting material than the first superconducting material layer 102, where the different superconducting material inherently has a lower superconducting energy gap than that of the first superconducting material layer 102. Alternatively, the same material may be used for the first superconducting material layer 102 and a second superconducting material layer 120 and / or third superconducting material layer 122, if a thickness of the second superconducting material layer 120 and / or third superconducting material layer 122 is smaller than a thickness of the first superconducting material layer 102.

[0109] The example of Fig. 6 illustrates one type of trapping element 200, but any other type of trapping element 200, in terms of e.g. shape of trapping material 104, coverage of the trapping material’s 104 surface area with the first insulating layer 106 etc., and / or total number of trapping elements 200 in the device may vary with embodiments of the invention where a second superconducting material layer 120 and / or a third superconducting material layer 122 are provided.

[0110] In an embodiment, the superconducting device 300 may comprise only one additional superconducting material layer, namely a second superconducting material layer 120, connected with the first superconducting material layer 102 either via its surface 112 or via its surface 114.

[0111] The presence of at least one additional superconducting material layer 120, 122 connected to the first superconducting material layer 102 may prevent even more the quasiparticles originally present in the first superconducting material layer 102 from reaching the Josephson junction.

[0112] Figure 7 shows an example of a superconducting device 400 comprising a first superconducting material layer 102 comprising a plurality of trapping elements 200 being embedded within the first superconducting material layer 102. The trapping elements 200 of the plurality of trapping elements 200 are as described previously. For clarity reasons, the localization areas 116a, 116b are not shown on Fig. 7 but they are present in the vicinity of each trapping element 200, as described previously for Figs. 2, 5 and 6.

[0113] Furthermore, a second superconducting material layer 120 and a third superconducting material layer 122 are provided in connection with the first superconducting material 102. The second and third superconducting material layers are provided as discontinuous material layers 120a, 120b, 122a, 122b. The discontinuity may be provided along the entire surface area of the second and / or third superconducting material layers 120, 122, such that separate portions 120a, 120b, 122a, 122b of the layers are provided, the discontinuity being in a direction parallel to the direction of the longitudinal axis of the first superconducting material layer 102. In different embodiments, one or both of the second superconducting material layer 120 or third superconducting material layer 122 may be present, with either one or both being provided as discontinuous material layers.

[0114] Figure 7 furthermore shows an example of a superconducting device 400 comprising or being connected to a Josephson junction 206.

[0115] The term “Josephson junction” in this text is used to refer to a (superconductor-insulator- superconductor) SIS junction that is provided in a superconducting device 100 or in connection with a superconducting device (that is separate from a possible SIS junction provided at an interface between the first superconducting material layer 102 and a trapping element).

[0116] At least one Josephson junction 206 may be formed at at least one edge of the first superconducting layer 102, in a direction substantially perpendicular to the longitudinal axis A of the first superconducting layer 102. A Josephson junction 206 may be provided in connection with a third surface 202 of the first superconducting layer 102 and / or in connection with a fourth surface 204 of first superconducting layer 102.

[0117] The presence of embedded trapping element(s) 200 within the first superconducting material layer 102 may prevent at least some of the quasiparticles originally present in the first superconducting material layer 102 from reaching the Josephson junction 206. The second superconducting material layer 120 and / or third superconducting material layer 122 may prevent even more of the quasiparticles originally present in the first superconducting material layer 102 from reaching the Josephson junction 206. A discontinuity in a second superconducting material layer 120a, 120b and / or third superconducting material layer 122a, 122b may yet prevent further quasiparticles originally present in the first superconducting material layer 102 from reaching the Josephson junction 206, as they may be unable to traverse along a second superconducting material layer 120a, 120b and / or third superconducting material layer 122a, 122b towards the Josephson junction 206.

[0118] The present invention may be especially advantageous in superconducting devices 100, 300, 400 comprising or being coupled to at least one Josephson junction 206, where at least one first superconducting material layer 102 of the superconducting device 100, 300, 400 is in tunnel contact (via a barrier / insulating layer) with at least one other superconducting material portion. The trapping element 200 may prevent at least some of the quasiparticles originally residing in the first superconducting material layer 102 of the superconducting device 100 from reaching the Josephson junction 206, and thus from tunneling through the Josephson junction 206.

[0119] A superconducting apparatus 500 may comprise a plurality of superconducting devices 100, 300, 400 wherein the separate superconducting devices 100, 400, 600 are coupled to each other via a Josephson junction 206.

[0120] A superconducting apparatus 500 may also comprise further components and / or be part of a larger superconducting arrangement, such as quantum computing device. In one embodiment, a quantum computing device may comprise a plurality of superconducting apparatuses 500 or superconducting devices 100, 300, 400 that are quantum devices, such as qubit devices. In particular, a qubit may be provided as a superconducting apparatus 500 comprising two superconducting devices 100, 300, 400 that are joined together by a Josephson junction.

[0121] Figure 8 shows one exemplary superconducting apparatus 500 comprising two superconducting devices 100, each comprising a first superconducting material layer 102, provided on a common substrate 002. Each superconducting device 100 comprises two trapping elements 200 embedded in their first superconducting material layer 102. For clarity reasons, the localization areas 116a, 116b are not shown on Fig. 8 but they are present in the vicinity of each trapping element 200, as described previously for Figs. 2, 5 and 6.

[0122] The superconducting devices 100 are coupled by a Josephson junction 206, so that the Josephson junction 206 is provided between the two superconducting devices 100. Only one of the superconducting devices 100 may comprise one or more trapping elements 200 or both of the superconducting devices 100 may comprise one or more trapping elements 200. One or both of the superconducting devices 100 may also comprise a second and / or a third superconducting material layer 120, 122.

[0123] Figure 9 shows a flow chart of a method of manufacturing a superconducting device (100, 300, 400) according to the invention.

[0124] The method comprises providing 010 at least one first superconducting material layer 102. Providing 010 the first superconducting material layer 102 is realized by depositing a superconducting material layer on a substrate, using standard deposition techniques for superconducting materials.

[0125] The method further comprises providing 012 at least one trapping element 200, wherein the trapping element 200 is embedded in the first superconducting material layer 102. Etching a portion of the first superconducting material layer 102 is first realized. The dimensions of the etched portion relate to the dimensions desired for the at least one trapping element 200. In a variant, the dimensions of the etched portion can be different that the dimensions desired for the trapping element 200.

[0126] Providing 012 of the trapping element 200 comprises providing a trapping material 104 and providing 014 at least a first insulating layer 106 positioned between at least a portion of the at least one trapping material 104 and the first superconducting material layer 102. Providing a trapping material 104 may be realized by providing a trapping material by standard deposition techniques for normal metal and / or for superconducting materials, in particular providing a trapping material layer.

[0127] Providing 014 at least a first insulating layer 106 may be realized by standard deposition techniques for insulating materials.

[0128] In some embodiments, the providing of the at least first insulating layer 106 may take place before and / or after the providing 012 of the at least one trapping material 104. For example, once the portion of the first superconducting material is etched, an insulating layer 106 may be deposited in the etched portion, so that the insulating layer 106 is deposited on the inner walls of the etched portion of the first superconducting material layer 102, before the trapping material 104 is deposited. The deposition of the insulating layer may be done on all of the inner walls of the etched portion or only on some of the inner walls of the etched portion. In a variant, the providing of the at least first insulating layer 106 may take place after the providing of the at least one trapping material 104.

[0129] In a variant, providing 014 at least a first insulating layer 106 may be realized by the growth of a native oxide at the bottom inner wall of the etched portion. Thus, providing 014 an insulating layer 106 before providing 012 the trapping material 104 does not require the deposition of an insulating layer 106 between the superconducting material layer 102 and the trapping material 104 by standard deposition techniques for insulating materials. In this variant, another insulating layer 106 may be provided at another inner wall of the etched portion and / or above the trapping material 104 using standard deposition techniques for insulating materials.

[0130] The providing 010 of the first superconducting material layer 102 may also be carried out simultaneously to the providing 012 of the trapping element(s) 200, to have the trapping elements 200 embedded in the first superconducting material layer 102.

[0131] In practice, the first superconducting material layer 102 is first at least partially provided by depositing onto a substrate 002. Following steps of etching and depositing may be carried out to alternately fabricate portions of the first insulating layer 106 and trapping material layer 104 to ultimately provide the superconducting device 100 with embedded trapping element(s) 200.

[0132] Further methods of manufacturing a superconducting device 100, 300, 400 may comprise additional steps of providing additional superconducting material layers, for example, a second superconducting material layer 120, optionally with a step of providing a third superconducting material layer 122. In these cases, if a second superconducting material layer 120 is provided beneath the first superconducting material layer 102, the second superconducting material layer 120 is first deposited onto the substrate before fabrication of the first superconducting material layer 102 and trapping element(s) 200. An additional superconducting material layer may also be provided on top of the previously fabricated remaining part of the superconducting device 100.

[0133] A method of manufacturing a superconducting device 100, 300, 400 according to the invention may further comprise providing at least one Josephson junction 206, if the superconducting device is to comprise a Josephson junction 206. At least one Josephson junction 206 may be formed at at least one side edge of the superconducting device 100,300, 400 in a direction substantially perpendicular to the longitudinal axis Ai of the first superconducting material layer 102. The Josephson junction 206 may be connected to the superconducting device 100, 300, 400 via one of the side surfaces 202, 204 of the superconducting device 100, 300, 400.

[0134] A method of manufacturing a superconducting apparatus 500 may comprise providing a plurality of superconducting devices 100, 300, 400 as described above and providing Josephson junctions 206 to couple each two adjacent superconducting devices of the plurality of superconducting devices to each other. A plurality of superconducting devices 100, 300, 400 may be fabricated simultaneously. The method may additionally comprise fabricating, simultaneously to fabricating the devices 100, at least one Josephson junction 206 to couple at least two adjacent superconducting devices 100, 300, 400 according to the invention to each other.

[0135] The invention has been explained above with reference to the aforementioned embodiments, and several advantages of the invention have been demonstrated. It is clear that the invention is not only restricted to these embodiments but comprises all possible embodiments within the spirit and scope of inventive thought and the following patent claims.

[0136] The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated.

Claims

CLAIMS1. A superconducting device (100, 300, 400) comprising: at least a first superconducting material layer (102) provided on a substrate (002) and, at least one trapping element (200) for reducing quasiparticle density in the first superconducting material layer (102), wherein the at least one trapping element (200) is embedded within the first superconducting material layer (102) and comprises at least one trapping material (104), characterized in that said trapping element (200) further comprises at least one first insulating layer (106), wherein said first insulating layer (106) is provided between at least a portion of the at least one trapping material (104) and the first superconducting material layer (102).

2. The superconducting device (100, 300, 400) of claim 1 , wherein a resistance of the first insulating layer (106) of the trapping element (200) is configured to reduce, in particular prevent, tunneling of quasiparticles from the trapping material (104) to the first superconducting material layer (102) via the first insulating layer (106), preferably wherein the resistance is at least above 100 Q / pm2, preferably above 500 Q / pm2.

3. The superconducting device (100, 300, 400) of any previous claim, wherein the trapping material (104) comprises a normal-conductivity metal material and / or a superconducting material, said superconducting material comprising a superconducting energy gap that is lower than a superconducting energy gap of the first superconducting material layer (102).

4. The superconducting device (100, 300, 400) of any previous claim, wherein the at least first insulating layer (106) is a single continuous insulating layer (106) or is formed from a plurality of discontinuous insulating layer portions.

5. The superconducting device (100, 300, 400) of any previous claim, wherein at a first- type interface (110) between the trapping material (104) and the first superconducting material layer (102), being an interface where the first insulating layer (106) is present, the resistance at the first-type interface is higher than a resistance at a second-type interface (108) between the trapping material (104) and the first superconducting material layer (102), being an interface where the first insulating layer (106) is not present.

6. The superconducting device (100, 300, 400) of any previous claim, wherein the trapping material has a shape comprising one or more surface(s) and wherein the at least first insulating layer (106) is provided at least partially on at least one or more surface(s).

7. The superconducting device (400) of any previous claim, further comprising a second superconducting material layer (120) coupled to at least a portion of the first superconducting material layer (102), wherein the second superconducting material layer (120) is configured to provide a superconducting energy gap that is lower than a superconducting energy gap of the first superconducting material layer (102).

8. The superconducting device (400) of claim 7, further comprising a third superconducting material layer (122), wherein the third superconducting material layer (122) is configured to provide a superconducting energy gap that is lower than a superconducting energy gap of the first superconducting material layer (102), wherein the first superconducting material layer (102) is sandwiched between the second superconducting material layer (120) and the third superconducting material layer (122).

9. The superconducting device (400) of claim 7 or claim 8, wherein at least one further layer is provided between the first superconducting material layer (102) and the second superconducting material layer (120) and / or between the first superconducting material layer (102) and the third superconducting material layer (122), in particular a further insulating layer.

10. The superconducting device (400) of any of claims 7 to 9, wherein the second superconducting material layer (120) and / or third superconducting material layer (122), if present, is a discontinuous material layer.

11. The superconducting device (100, 300, 400) of any previous claim, wherein the first superconducting material layer (102) comprises one or more region(s) (116a, 116b, 116c), in particular localization areas, where the superconducting energy bandgap is lower than the superconducting energy bandgap of the rest of the first superconducting material layer (102), said one or more region(s) (116a, 116b, 116c) being located in the proximity of the second-type interface (108), said second-type interface being between a surface of the at least one trapping element (104) and the first superconducting material layer (102).

12. The superconducting device (100, 300, 400) of claim 11 , wherein the interface between the one or more regions (116a, 116b, 116c) of the first superconductingmaterial (102) with a lower superconducting bandgap than the superconducting bandgap of the first superconducting material (102) and the at least one trapping element (104) comprises a resistance lower than the resistance of the interface between the at least first tunneling layer (106) of the trapping element (200) and the first superconducting material layer (102).

13. The superconducting device (100, 300, 400) of claim 11 or 12, wherein said one or more regions (116a, 116b, 116c) of the first superconducting material layer (102) with a lower superconducting bandgap compared to the rest of the first superconducting material layer (102) is / are configured to localize the quasiparticles within the one or more regions (116a, 116b, 116c) of the first superconducting material layer (102), in particular the quasiparticles present in the trapping element (200) tunneling back to the first superconducting material layer (102).

14. The superconducting device (100, 400) of any previous claim, comprising a plurality of trapping elements, each trapping element (200) of the plurality of trapping elements comprising:- at least one trapping material (104) and,- at least a first insulating layer (106), wherein each trapping element (200) of the plurality of trapping elements is embedded within the first superconducting material layer (102), such that the first superconducting material layer (102) is in contact with the first insulating layer (106) of each of the trapping element (200) of the plurality of trapping elements.

15. The superconducting device (100, 400) of claim 14, wherein the trapping elements (200) of the plurality of trapping elements are distributed within the first superconducting material layer (102) such that each trapping element (200) of the plurality of trapping elements are separated from each other.

16. A superconducting apparatus (500) comprising a plurality of superconducting devices of any of claims 1 -15, wherein at least two adjacent superconducting devices (100, 300, 400) are coupled to each other via a Josephson junction (206).

17. The superconducting apparatus (500) of claim 16, wherein at least one Josephson junction (206) is formed at at least one side edge (212, 214) of at least one of the superconducting devices (100, 300, 400), in a direction substantially parallel to a longitudinal axis of the first superconducting material layer (102) of the superconducting device (100, 300, 400).

18. A method of manufacturing a superconducting device (100, 300, 400) according to any of claims 1 to 15, the method comprising: providing (010) at least one first superconducting material layer (102) on a substrate (002), providing (012) at least one trapping element (200) comprising a trapping material (104), wherein the trapping element (200) is embedded in the first superconducting material layer (102), characterized in that the step of providing (012) at least one trapping element (200) comprises providing (014) at least a first insulating layer (106) positioned between at least a portion of the trapping material (104) and the first superconducting material layer (102).

19. A method of manufacturing a superconducting apparatus (500), the method comprising manufacturing a plurality of superconducting devices according to the method of claim 18, the method additionally comprising providing at least one Josephson junction (206) to couple at least two adjacent superconducting devices (100, 300, 400) of the plurality of superconducting devices to each other.

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