Josephson junction quantum mechanical device with increased critical current

Abstract

Disclosed is a Josephson junction quantum mechanical device (200) comprising a first electrode (211) arranged on a substrate (201) and having a first elongated arm (221), and a second electrode (212) arranged on the substrate and comprising a second elongated arm (222). The first elongated arm and the second elongated arm extend toward each other to define an area of overlap (250). Furthermore, the first elongated arm and the second elongated arm each comprise, at the area of overlap, a respective first lateral flange (221 A, 222A). The first lateral flange (221 A) of the first elongated arm extends along a first lengthwise part (P1) of the first elongated arm and along a second lengthwise part (P2) of the second elongated arm, whereas the first lateral flange (222A) of the second elongated arm extends along a third lengthwise part (P3) of the second elongated arm and along a fourth lengthwise part (P4) of the first elongated arm. Thereby, the area of overlap is defined to comprise a surface area larger than a product of the respective widths of the first elongated arm and second elongated arm.

Description

JOSEPHSON JUNCTION QUANTUM MECHANICAU DEVICE WITH INCREASED CRITICAL CURRENTTECHNICAL FIELD

[0001] The present disclosure relates to a Josephson junction quantum mechanical device comprising one or more Josephson junctions, which may find application in e.g. the field of quantum computing.BACKGROUND

[0002] Josephson junction quantum mechanical devices are quantum mechanical devices that comprise superconducting circuits with one or more Josephson junctions, from which they derive their macroscopic quantum mechanical properties. Such devices find application within the fields of e.g. quantum computing and high precision measurement and sensing. Within the field of quantum computing in particular, Josephson junctions are used to implement qubits for performing quantum computations and parametric amplifiers for inferring the quantum states of qubits.

[0003] A Josephson junction comprises two overlapping superconducting electrodes separated by a thin insulating barrier layer, through which a supercurrent can tunnel without resistance at cryogenic temperatures. The maximum supercurrent that can tunnel through the barrier layer without inducing a voltage is known as the critical current. The magnitude of the critical current is in part determined by the area of overlap between the two superconducting electrodes.

[0004] Josephson junctions are typically manufactured using angular evaporation, which is also known as "shadow evaporation" and as the "Niemeyer-Dolan technique". In angular evaporation, (superconducting) material is deposited on a substrate in one or more evaporation directions. A patterned resist placed on the substrate results in the material being deposited on the substrate in patterns that are dependent on the evaporation direction that is used. By depositing material from a crucible from different evaporation directions over several iterations, a multilayered structure making up the Josephson junction is obtained. The critical current of the Josephson junction may be engineered by dimensioning a specific area of overlap between the two superconducting electrodes making up theJosephson junction.

[0005] The critical current is an important parameter of a Josephson junction that determines its characteristics and, by extension, the characteristics of the Josephson junction quantum mechanical device that comprises it. In case of superconducting qubits, for example, the critical current of one or more Josephson junctions determines the qubit's energy levels and transition frequencies between quantum states. Certain types of qubits, such as fluxonium qubits, require multiple Josephson junctions with varying critical currents for their operations. For Josephson travelling wave parametric amplifiers (JTWPAs), the critical currents of Josephson junctions determine e.g. the JTWPA's power handling capacity.

[0006] Because angular evaporation is dependent on 'shadows' being cast by a patterned resist to form predefined patterns of material on a substrate, this fabrication technique is limited with respect to fabricating Josephson junctions with enlarged electrode dimensions and correspondingly enlarged areas of overlap and critical currents. A patterned resist with oversized trenches etched therein will result in vaporous material being deposited onto undesired areas on the substrate, which will result in a short circuit between the superconducting electrodes making up the Josephson junction.

[0007] The above-described limitation of angular evaporation can be partially overcome by e.g. increasing the thickness of the patterned resist or by altering the angle of the evaporation direction relative to the substrate. These countermeasures, however, result in an increased degree of manufacturing complexity with the manufacturing process being more susceptible to unintended variations of e.g. the angle of the crucible and the thickness of the patterned resist. As such, they generally lead to increased lead times and decreased manufacturing yield.

[0008] A further disadvantage of these countermeasures is their poor scalability when manufacturing Josephson junction quantum mechanical devices that comprise multiple Josephson junctions with varying dimensions, areas of overlap and corresponding critical currents. Fabricating such a device by constantly varying the resist layer thicknesses and / or angle of the crucible is undesirable, because it introduces additional sources of uncertainty into the manufacturing process. In general, manufacturing parameters (including the thickness of the resist layer and the angle of the crucible) are altered as little as possible and preferably kept constant where possible.

[0009] The document entitled "Bridge-free fabrication process for AI / AI0)AI Josephson junctions" by Ke Zhang et al. discusses the fabrication of different-sized Al / Al Ox / Al Josephson junctions by using a bridge-free technique, in which a single-layer E-beam resist polymethyl methacrylate (PMMA) is exposed at low accelerate voltage (below 30 kV) and the size of junction can be varied.

[0010] The document entitled "Phonon engineering of atomic-scale defects in superconducting quantum circuits" by Mo Chen et al. discloses an approach that seeks to modify the properties of TLS through nanoscale-engineering. This is achieved by periodically structuring the host material, forming an acoustic bandgap that suppresses all microwave-frequency phonons in a GHz-wide frequency band around the operating frequency of a transmon qubit superconducting quantum circuit.

[0011] US2022140223A1 discloses methods, apparatuses, and devices for Josephson junction preparation including: obtaining a first pattern structure for generating a first Josephson junction of a first type and a plurality of second pattern structures for generating a plurality of second Josephson junctions of a second type; evaporating a material on the first pattern structure and the plurality of second pattern structures based on a first evaporation direction to generate a first electrode layer for implementing information transmission; forming an insulating layer on the first electrode layer, the insulating layer including a compound corresponding to the material; evaporating the material on the first pattern structure and the plurality of second pattern structures based on a second evaporation direction to generate a second electrode layer for implementing information transmission; and forming the first Josephson junction and the plurality of second Josephson junctions.

[0012] The object of the present disclosure is to provide a means with which one or more of the above-described drawbacks of known Josephson junction quantum mechanical devices is obviated or abated. More specific, an object of the present disclosure is to provide a Josephson junction quantum mechanical device comprising at least one Josephson junction, of which the area of overlap between the two electrodes may be arbitrarily selected, while avoiding excessively altering the thickness of the resist layer and avoiding excessively varying the angle of the crucible used for depositing superconducting material.SUMMARY

[0013] In accordance with a first aspect, the above object is achieved with a Josephson junction quantum mechanical device comprising a first electrode arranged on a substrate and having a first elongated arm, and a second electrode arranged on the substrate and comprising a second elongated arm. The first elongated arm and the second elongated arm extend toward each other to define an area of overlap. Furthermore, the first elongated arm and the second elongated arm each comprise, at the area of overlap, a respective first lateral flange. The first lateral flange of the first elongated arm extends along a first lengthwise part of the first elongated arm and along a second lengthwise part of the second elongated arm, whereas the first lateral flange of the second elongated arm extends along a third lengthwise part of the second elongated arm and along fourth lengthwise part of the first elongated arm. Thereby, the area of overlap between the first electrode and second elongated electrode is defined to comprise a surface area larger than a product of the respective widths of the first elongated arm and second elongated arm.

[0014] The above Josephson junction quantum mechanical device comprises the advantage that a critical current of one or more Josephson junctions of said device may be engineered to comprise an arbitrarily selected value, without risk of a short circuit occurring between the electrodes and without further complicating its manufacturing process or making it more susceptible to manufacturing faults.

[0015] In accordance with preferred embodiments of the Josephson junction quantum mechanical device, at least one of the first electrode and the second electrode has been formed using an angular evaporation fabrication technique.

[0016] In accordance with further preferred embodiments of the Josephson junction quantum mechanical device, at least one of the first lateral flange of the first elongated arm and the first lateral flange of the second elongated arm comprises a polygon shape, preferably a substantially rectangular shape.

[0017] In accordance with further preferred embodiments of the Josephson junction quantum mechanical device, the first lateral flange of the first or second elongated arm protrudes in a direction non-parallel to a lengthwise direction of said first or second elongated arm.

[0018] In accordance with further preferred embodiments of the Josephson junction quantum mechanical device, the first elongated arm and the second elongated arm each comprise, at the area of overlap, a respective second lateral flange opposite the first lateral flange.

[0019] In accordance with further preferred embodiments of the Josephson junction quantum mechanical device, the second lateral flange of the first elongated arm extends along a fifth lengthwise part of the first elongated arm and along a sixth lengthwise part of the second elongated arm. In these embodiments, the second lateral flange of the second elongated arm extends along a seventh lengthwise part of the second elongated arm and along an eighth lengthwise part of the first elongated arm.

[0020] In accordance with further preferred embodiments of the Josephson junction quantum mechanical device, at least one, or both, of the first elongated arm and the second elongated arm comprises a respective free end that extends beyond the area of overlap and beyond the first lateral flange of said first elongated arm and / or second elongated arm.

[0021] In these embodiments, an increased consistency of a critical current of a Josephson junction comprised by the Josephson junction quantum mechanical device is achieved.

[0022] In accordance with further preferred embodiments of the Josephson junction quantum mechanical device, the first elongated arm and the second elongated arm are oriented relative to one another such that their respective lengthwise directions are non-parallel to one another.

[0023] In accordance with further preferred embodiments of the Josephson junction quantum mechanical device, the first electrode and the second electrode form at least a portion of a superconducting qubit.

[0024] In accordance with further preferred embodiments of the Josephson junction quantum mechanical device, the first electrode and the second electrode form at least a part of a transmission line of a Josephson travelling wave parametric amplifier (JTWPA).

[0025] In accordance with further preferred embodiments of the Josephson junction quantum mechanical device, the substrate comprises at least one of silicon, silicon dioxide, silicon nitride, sapphire, gallium arsenide, quartz, magnesium oxide, lithium niobate, lanthanum aluminate, strontium titanate, boron nitride, hafnium dioxide.

[0026] In accordance with further preferred embodiments of the Josephson junction quantum mechanical device, at least one of the first and second electrodes comprises at least one of aluminium, niobium, tantalum, lead, tin and molybdenum.

[0027] In accordance with a second aspect, the above object is furthermore achieved with a method of manufacturing a Josephson junction quantum mechanical device. The method comprises the steps of providing a substrate having a resist layer arranged thereon and patterning the resist layer to form, in the resist layer, a first elongated trench and a second elongated trench. The first elongated trench and the second elongated trench extend to intersect one another at an intersection. The method furthermore comprises the steps of depositing a first layer of superconducting material on the patterned resist layer, and depositing a second layer of superconducting material on the patterned resist layer. The step of patterning the resist layer furthermore comprises forming, at the intersection between the first and second trenches, a first recess that extends laterally along a first part of the first elongated trench and along a first part of the second elongated trench.

[0028] In accordance with preferred embodiments of the above method, patterning the resist layer further comprises forming, at the intersection between the first and second trenches, a second recess opposite the first recess, wherein the second recess extends laterally along a second part of the first elongated trench and along a second part of the second elongated trench.

[0029] In accordance with further preferred embodiments of the above method, patterning the resist layer further comprises forming at least one, or both, of first elongated trench and the second elongated trench to extend beyond the intersection and beyond the first recess.

[0030] In accordance with further preferred embodiments of the above method, at least one of depositing the first layer of superconducting material and depositing the second layer of superconducting material, comprises usage of an angular evaporation fabrication technique.

[0031] In accordance with a third aspect, the object of the present disclosure is achieved with a method for performing a quantum computation. The method for performing a quantum computation comprises usage of a Josephson junction quantum mechanical device in accordance with any one of the here above-described embodiments.

[0032] In accordance with a fourth aspect, the object of the present disclosure is achieved with a method for performing signal processing. The method for signal processing comprises usage of a losephson junction quantum mechanical device in accordance with any one of the here above-described embodiments.LIST OF FIGURES

[0033] Here below, the present invention is elucidated with reference to the appended drawing, in which:

[0034] FIG. 1 shows a losephson junction quantum mechanical device in accordance with the known prior-art;

[0035] FIG. 2 shows perspective view of a first exemplary embodiment of losephson junction quantum mechanical device in accordance with the present disclosure;

[0036] FIG. 3A shows a perspective view of a second exemplary of a (part of a) losephson junction quantum mechanical device in accordance with the present disclosure;

[0037] FIG. 3B shows a detail of the losephson junction quantum mechanical device of FIG. 3A;

[0038] FIG. 4A to FIG. 4D illustrate a workpiece undergoing consecutive manufacturing steps to manufacture a losephson junction quantum mechanical device;

[0039] FIG. 5 shows a workpiece that is an alternative to the workpiece shown in FIG. 4B, in accordance with certain embodiments;

[0040] FIG. 6A to FIG. 6D illustrate a further workpiece undergoing consecutive manufacturing steps to manufacture a losephson junction quantum mechanical device comprising multiple losephson junctions; and

[0041] FIG. 7A to FIG. 7D illustrate a yet further workpiece undergoing consecutive manufacturing steps to manufacture a losephson junction quantum mechanical device comprising multiple losephson junctions.DETAILED DESCRIPTION

[0042] In the detailed description here below, various embodiments of a Josephson junction quantum mechanical device are elucidated with reference to the appended drawing. It will be understood that these embodiments do not limit the scope of the present disclosure, which is defined by the features recited by the appended independent claims and, at least in certain jurisdictions, their equivalents.

[0043] FIG. 1 shows an example of a Josephson junction quantum mechanical device 100 in accordance with the known prior art. The Josephson junction quantum mechanical device 100 comprises a Josephson junction 120 with a first electrode 121 and a second electrode 122 that overlap to form the Josephson junction 120. An insulating barrier layer (not shown) is arranged between the first electrode 121 and the second electrode 122.

[0044] The first electrode 121 and the second electrode 122 each comprise an elongated body having substantially constant widths along their respective lengths. An area of overlap between the first electrode 121 and the second electrode 122 that defines the factual Josephson junction 120 is hence defined by the product of these respective widths.

[0045] The first electrode 121 and the second electrode 122 moreover extend from respective capacitive plates 112, 113, that may be comprised by a qubit (not shown).

[0046] FIG. 2 shows a first exemplary embodiment of a Josephson junction quantum mechanical device 200.

[0047] The Josephson junction quantum mechanical device 200 comprises a substrate 201. The substrate 201 may comprise silicon, sapphire, or any other suitable material known in the art.

[0048] A first electrode 211 and a second electrode 212 are arranged on a top surface of the substrate 201. The first electrode 211 and the second electrode 212 each comprise a respective elongated arm 221, 222 that defines the respective lengths of the first electrode 211 and the second electrode 212. In accordance with various embodiments, the elongated arms 221, 222 of the first electrode 211 and the second electrode 212 may each comprise an overall length of e.g. 6 to 12 pm.

[0049] The elongated arms 221, 222 may optionally moreover comprise respective base sections 227, 228 from which the remainders of the elongated arms 221, 222 extend. In accordance with various embodiments, the base sections 227, 228 may be comprised by, or connected to, capacitive plates (see reference numerals 112 and 113 in FIG. 1) of a superconducting qubit. Alternatively, the base sections227, 228 may be common base sections connecting the electrodes 211, 212 to yet further electrodes of additional Josephson junctions (not shown) to form a chain of Josephson junctions. In accordance with various embodiments, the base sections 227, 228 may comprise a width of 0.5 to 1.5 pm and an arbitrarily selected length that constitutes no more than a fraction of the overall length of the elongated arms 221, 222 of the first and second electrodes 211, 212.

[0050] The respective elongated arms 221, 222 of the of the first electrode 211 and the second electrode 212 each comprise a width of e.g. 0.1 to 0.3 pm, in accordance with various embodiments.

[0051] The elongated arm 221 of the first electrode 211 and the elongated arm 222 of the second electrode 212 extend toward each other, such they overlap with one another at an area of overlap 250. The first elongated arm 221 and the second elongated arm 222 may be oriented relative to one another, such that their respective lengthwise directions are non-parallel to one another. An angle between the first elongated arm 221 and the second elongated arm may be 90 degrees. An isolating barrier layer may be arranged in between the first elongated arm 221 and the second elongated arm 222 at least at the area of overlap 250. Thereby, a Josephson junction 220 is defined.

[0052] The first elongated arm 221 and the second elongated arm 222 moreover each comprise respective first lateral flanges 221 A, 222A. The first lateral flange 221 A is electrically connected to the first elongated arm 221 and the first lateral flange 222A is electrically connected to the second elongated arm 222. The first lateral flange 221 A is preferably integrally formed with the first elongated arm 221 of the first electrode 211, and the first lateral flange 222A is preferably integrally formed with the elongated arm 222 of the second electrode 212. The two elongated arms 221, 222 including their respective first lateral flanges 221 A, 222A are preferably integrally formed using angular evaporation. An exemplary method for forming the first and second arms 221, 222 including the first lateral flanges 221 A, 222A is elucidated here below with reference to FIG. 4A to 4D.

[0053] The first lateral flanges 221 A, 222A are arranged at the area of overlap 250. Each one of the two first lateral flanges 221 A, 222A extends along no more than respective lengthwise parts Pi, P3 of the elongated arm 221, 222 of the first and second electrodes 211, 212. As can be discerned from FIG. 2, the first lateral flange 221 A of the first elongated arm 221 extends along a first lengthwise part Pi ofthe first elongated arm 221 and along a second lengthwise part P2of the second elongated arm 222. The first lateral flange 222A of the second elongated arm 222 extends along a third lengthwise part P3 of the second elongated arm 222 and along fourth lengthwise part P4of the first elongated arm 222. From FIG. 2 it can moreover be discerned that the effective area of overlap between the first electrode 211 and second electrode 212 is defined to comprise a surface area larger than a product of the respective widths of the first elongated arm 221 and the second elongated arm 222.

[0054] The first lateral flanges 221 A, 222A may extent from only one side of each of the two elongated arms 221, 222. The first lateral flange 221A may extend on the side of the first elongated arm 221 closest to the free end of the second elongated arm 222 and / or the second lateral flange 222A may extend on the side of the second elongated arm 222 closest to the free end of the first elongated arm 221. The first lateral flange 221 A may extent from two sides of the first elongated arm 221 and / or the second lateral flange 222A may extent from two sides of the second elongated arm 222.

[0055] The two elongated arms 221, 222 may cross at a substantially right angle. The second lengthwise part P2and the third lengthwise part P3may have a length larger than the width of the first elongated arm 221. The first lengthwise part P and fourth lengthwise part P4may have a length larger than the width of the second elongated arm 222. The area of overlap may be substantially equal to the minimum of P and P4times the minimum of P2and P3plus the product of P4with the width of the first elongated arm 221 plus the product of P2with the width of the second elongated arm 222. The relevant overlap may be the overlap of the first elongated arm 221 and the first lateral flange 221 A of the first elongated arm 221 with the second elongated arm 222 and the first lateral flange 222A of the second elongated arm 222.

[0056] The overlap region may substantially correspond to the union of the following regions : a portion of the first elongated arm 221, a portion of the second elongated arm 222 and a rectangular region formed in-between the first elongated arm 221 and the second elongated arm 222 at the side of both their free ends.

[0057] It will be appreciated that the here above-described configuration of the respective first lateral flanges 221 A, 222A results in the effective area of overlap 250 between the first and second electrodes211, 212 (including the first lateral flanges 221A, 222A) to be enlarged, as indicated by the dottedborder of the area of overlap 250 in FIG. 2. In accordance with various embodiments, the area of overlap 250 may comprise a surface area of e.g. 1.5 to 3.0 m2. This is considerably larger than if this area of overlap 250 was to be defined solely by the product of the respective diameters of the elongated arms 221, 222 of the first and second electrodes 211, 212 (i.e. 0.04 pm2), as is the case in the prior-art Josephson junction 120 in FIG. 1.

[0058] In accordance with various embodiments, the two first lateral flanges 221 A, 222A may each comprise a polygon shape, preferably a substantially rectangular shape. Such a polygon shape or rectangular shape may optionally comprise rounded comers and / or edges.

[0059] In accordance with various embodiments, the first and second electrodes 211, 212 may be formed using angular evaporation. In these embodiments, the device 200 may moreover comprises a first residue portion 261 and a second residue portion 262 of superconducting material that may be arranged in the vicinity the base sections 227, 228 of the first and second electrodes 211, 212.

[0060] The above-described configuration of the first lateral flanges 221 A, 222A (having dimensions larger than the product of the respective diameters of the elongated arms 221, 222) advantageously results in the residue portions 261, 262 not extending to the intersection between the first and second electrodes 211, 212, where the residue portions 261, 262 may result in a short circuit.

[0061] The first residue portion 261 is arranged in the general vicinity of the second electrode 212 and the second residue portion 262 is arranged in the general vicinity of the first electrode 211. The residue portions 261, 262 are byproducts inherent to the fabrication technique (angular evaporation) used to fabricate the device 300, in accordance with various embodiments. This fabrication technique will be further elucidated here below with reference to FIG. 4A to FIG. 4D. With reference to these figures, it will be explained that the presence of the first and second residue portions 261, 262 will result in a short circuit between the first electrode 211 and the second electrode 212, if the first lateral flanges 221 A, 222A are absent and instead the diameters of the elongated arms 221, 222 are dimensioned to achieve an enlarged area of overlap.

[0062] One or both of the first electrode 211 and the second electrode 212 may furthermore comprise an "antenna" 204a, 204b, which is a distal free end 204a, 204b of the elongated electrode arms 221,222. The free ends 204a, 204b of the elongated electrode arms 221, 222 may be located opposite the base sections 227, 228, relative to the area of overlap 250 and the lateral flanges 221 A, 22A. The free ends 204a, 204b may be considered parts of the elongated electrode arms 221, 222 that do not comprise the lateral flanges 221 A, 22A, but extend beyond the lateral flanges and the area of overlap 250, which is defined by them.

[0063] The free ends 204a, 204b result in the advantage that, when a Josephson junction quantum mechanical device comprising a plurality of Josephson junctions is manufactured, a constant area of overlap 250 between the first electrode 211 and the second electrode 212 is obtained, regardless of the orientation of the individual Josephson junctions relative to the crucible. This will be elucidated further here below with reference to FIG. 5A to 5D, and more in particular with reference to FIG. 6A to 6D.

[0064] FIG. 3A and FIG. 3B show an additional exemplary embodiment of a Josephson junction quantum mechanical device 300.

[0065] Like the foregoing embodiment, the Josephson junction quantum mechanical device 300 comprises a substrate 301 having a first electrode 311 and a second electrode 312 arranged thereon. The first electrode 311 comprises an elongated arm 321 that defines a length of the first electrode 311 and, in accordance with various embodiments, may optionally comprise an enlarged base section 327. Similarly, the second electrode 312 comprises an elongated arm 322 that defines a length of the second electrode 312 and said elongated arm 322 may likewise comprise an optional base section 438. The elongated arms 321, 322 constituting the first and second electrodes 311, 312 may each comprise a length of e.g. 6.0 - 12.0 pm.

[0066] The elongated arms 321, 322 of the first and second electrodes 311, 312 extend toward one another such that the first and second electrodes 311, 312 overlap with one another at an area of overlap 350. In FIG. 4A, the area of overlap 350 is indicated by the dotted border. Like in the foregoing embodiment, the elongated arm 321 of the first electrode 311 and the elongated arm 322 moreover comprise respective first lateral flanges 321 A, 322A. The two respective first lateral flanges 321 A, 322A each extend along no more than respective lengthwise parts of the elongated arms 321 , 322 of the first electrode 311 and the second electrode 312. Said respective parts being located at the intersectionof the elongated arms 321, 322. In contrast to the foregoing embodiment, said lengthwise parts extend well beyond the area of overlap 350.

[0067] Referring now specifically to FIG. 3B, the respective elongated arms 321, 322 of the first and second electrodes 311, 312 moreover comprise respective second lateral flanges 321B, 322B. The second lateral flange 32 IB of the elongated arm 321 of the first electrode 311 is arranged opposite the first lateral flange 321 A, and the second lateral flange 322B of the elongated arm 322 of the second electrode 312 is arranged opposite is located opposite the first lateral flange 322A. In accordance with various embodiments, the second lateral flanges 321B, 322B may comprise dimensions similar or identical to those of the first lateral flanges 321 A, 322A.

[0068] The second lateral flange 32 IB may be integrally connected to the elongated arm 321 of the first electrode 311. The second lateral flange 322B may be integrally connected to the elongated arm 322 of the second electrode 312. The second lateral flanges 32 IB, 322B are preferably formed with the elongated arms 321, 322 by means of angled evaporation. The second lateral flange 321B may be electrically coupled to the first elongated arm 321 and the second lateral flange 322B may be electrically coupled to the second elongated arm 322.

[0069] The second lateral flange 32 IB of the elongated arm 321 of the first electrode 311 may extend along a fifth lengthwise part P5 of the first elongated arm 321 of the first electrode 311, and along a sixth lengthwise part P6 of the second elongated arm 322 of the second electrode 312. Likewise, the second lateral flange 322B may extend along a seventh lengthwise part P7 of the elongated arm 322 of the second electrode 312, and along an eight lengthwise part P8 of the elongated arm 311 of the first electrode 311.

[0070] It will be appreciated that the here above-described configuration of the respective first lateral flanges 321 A, 322A and second lateral flanges 32 IB, 322B results in the effect area of overlap 350 between the first and second electrodes 311, 312 to be effectively enlarged, as indicated by the dotted border of the area of overlap 350 in FIG. 3A and FIG. 3B.

[0071] It is noted here that the embodiment of the Josephson junction quantum mechanical device 300 of FIG. 3A and FIG. 3B does not comprise the optional feature of an "antenna", i.e. a free end of the elongated arms 321, 322 that extends beyond the lateral flanges 321A, 321B, 322A, 322B.

[0072] FIG. 4A to FIG. 4B show subsequent steps of a method for fabricating a Josephson junction quantum mechanical device in accordance with various embodiments.

[0073] Referring now specifically to FIG. 4A, a workpiece 400 may be provided comprising a substrate 401 and a layer of resist material 408. The substrate 401 may comprise e.g. silicon, sapphire or any other suitable material known within the art. The resist material 408 may be applied to a first surface of the substrate 401 and may be either a positive resist material or a negative resist material.

[0074] Now referring to FIG. 4B, the layer of resist material 408 of the workpiece 400 may thereafter be patterned to form a first elongated trench 441 and a second elongated trench 442. In the first elongated trench 441 and the second elongated trench 442, the resist material 408 is removed using any one of the methods known in the art to thereby expose the substrate 401 underneath.

[0075] The first elongated trench 441 may extend from a respective beginning point 441 A to a respective end point 441B. Likewise, the second elongated trench 442 extends from a respective beginning point 442A to a respective end point 442B, such that the first elongated trench 441 and the second elongated trench 442 intersect one another at an intersection 460. The first elongated trench 441 and the second elongated trench 442 may respectively comprise relatively increased widths at the beginning points 441 A, 442A for forming base sections of electrodes (see FIG. 2, reference numerals 227 and 228).

[0076] The layer of resist material 408 is moreover patterned to comprise, at said intersection 460, at least one first recess 461 that extends along part the first elongated trench 441 and along part the second elongated trench 442. As such, the intersection 460 between the first and second trenches 441, 442 is effectively enlarged by means of the first recess 461 to comprise a surface area larger than the product of the respective widths of the first and second elongated trenches 441, 442.

[0077] Referring now to FIG. 4C, the workpiece 400 having the patterned layer may thereafter have superconducting material (e.g. niobium) deposited thereon, preferably by means of angular evaporation, to thereby form a first layer of superconducting material 431. Vaporous superconducting material may be deposited from a crucible (not shown) from a deposition direction - which is indicated by the arrows on the left-handed side of FIG. 4C - at an angle relative to a plane of the substrate 401. In accordancewith various embodiment, said angle of the deposition direction relative to a plan may comprise any value within the range of 30° to 45° relative to a plane in which the substrate 401 lies.

[0078] Due to the presence of the patterned layer of resist material 408, the vaporous superconducting material only reaches the substrate 401 in certain areas, while in other areas the resist material 408 casts a 'shadow' in which no vaporous superconducting material reaches the substrate. In FIG. 4C, areas in which the resist material 408 casts a shadow are indicated by reference numerals Si, S2, S3 and S4.

[0079] Areas in which the vaporous superconducting material does reach the substrate 401 include a substantial length of the second elongated trench 441 and a zone within the first recess 461 (on the right of the first recess 461 in FIG. 4C). Moreover, a residue portion 461 of superconducting material is deposited in the second elongated trench 442 near the beginning point (see moreover FIG. 2, reference numeral 261). It will be appreciated that this residue portion would result in a short circuit between the two electrodes constituting the Josephson junction if it were to extend to the intersection 460, which could be the case if the width of the second elongated trench were enlarged to obtain a Josephson junction with a higher critical current.

[0080] Following the deposition of the first layer of superconducting material 431, a non-conductive barrier layer may be formed on the first layer of superconducting material 431. The non-conductive barrier layer may be an oxide layer. For example, in embodiments in which the first layer of superconducting material 431 comprises aluminium, the non-conductive barrier layer may comprise aluminium oxide. In these embodiments, the non-conductive barrier layer may be formed by briefly introducing oxygen into an enclosure that houses the workpiece 400, which is otherwise kept hermetically closed.

[0081] After the first layer of superconducting material 431 has been deposited onto the workpiece 400, the workpiece 400 may then be rotated relative to a crucible (not shown) to then deposit a second layer of superconducting material 432. In FIG. 4D, the arrows at the bottom side of the figure pointing toward the workpiece 400 indicate the deposition angle for applying vaporous superconducting material to the workpiece 400. This deposition angle may comprise any value within the range of 30° to 45° relative to the plane of the substrate 401 of the workpiece 400.

[0082] Again, the patterned resist layer 408 results in the vaporous superconducting material reaching the substrate 401 only within certain areas. These areas include a substantial part of the length of the second elongated trench 442, including the intersection 460 and part of the first recess 461.

[0083] In other areas, the patterned resist layer 408 casts 'shadows' that prevent the vaporous superconducting material from reaching the substrate 401. In FIG. 4D, at least some of these shadows are indicated by reference numerals S5, S6, S7, S8, S9.

[0084] Furthermore, a residue portion 446 is deposited within the part having the enlarged with of second elongated trench 442. It will be appreciated that this residue portion 446 does not extend to the intersection 460, where it may potentially result in a short circuit between the electrodes that are constituted by the first and second layers of superconducting material 431, 432.

[0085] After the second conducting layer 432 has been deposited onto the workpiece 400 as described here above, the layer of resist material 408 may be removed from the workpiece 400 to thereby obtain e.g. the embodiment of the Josephson junction quantum mechanical device 300 of FIG. 3.

[0086] Reference is made now to FIG. 5, which shows a workpiece 500 having a substrate 501 and a layer of resist material 508. The workpiece 500 may correspond to a state of the workpiece 400 depicted in FIG. 4B. The workpiece 500 may be subjected to subsequent manufacturing steps that have been described here above with reference to FIG. 4C and 4D.

[0087] The workpiece 500 comprises a substrate with a layer of resist material 508 arranged thereon. A first elongated trench 541 and a second elongated trench 542 are etched into the resist material 508, exposing the substrate underneath. The first elongated trench 541 and a second elongated trench 542 intersect one another. A first recess 561 is etched into the resist material 508 at the intersection between the first elongated trench 541 and a second elongated trench 542. The first recess 561 extends along the first elongated trench 541 and along the second elongated trench 542.

[0088] The workpiece 500 moreover comprises a second recess 562, a third recess 563 and a fourth recess 564 etched into the resist material 508. The second recess 562, the third recess 563 and the fourth recess 564 are likewise arranged at the intersection between the first elongated trench 541 and the second elongated trench 542. The second recess 562, the third recess 563 and the fourth recess 564 extend along respective parts of the first elongated trench 541 and the second elongated trench 542.

[0089] It will be appreciated that, by patterning the layer of resist material 508 as depicted in FIG. 5, a Josephson junction with a yet further increased critical current may be obtained, without altering the thickness of the layer of resist material 508 or the angular evaporation deposition angles, while simultaneously avoiding a short circuit between the two electrodes constituting the Josephson junction.

[0090] The above-described various embodiments of Josephson junction quantum mechanical devices may be comprised by, for example, a quantum processing unit (QPU) comprising a plurality of superconducting qubits, each comprising one or more Josephson junction devices. These qubits may be fluxonium qubits comprising multiple Josephson junctions with varying critical currents. Alternatively, the embodiments of Josephson junction quantum mechanical devices may be comprised by a Josephson junction travelling wave parametric amplifier (JTWPA) comprising a chain of Josephson junctions.

[0091] FIG. 6A to FIG. 6D show subsequent steps of manufacturing a Josephson junction quantum mechanical device, in accordance with various embodiments.

[0092] FIG. 6A shows a top-down view of a workpiece 600. The workpiece 600 comprises a substrate with a layer of resist material 608 arranged on atop surface of the substrate. A meandering pattern 601' has been etched into the layer of resist material 608, exposing the substrate underneath. The meandering pattern 601' comprises recesses 602a, 602b, 602c and 602d, which in the present exemplary embodiment are approximately square. The recesses 602a, 602b, 602c and 602d are interconnected by elongated trenches 603a, 603b, 603c, 603d and 603e etched into the resist material 608. In contrast to the foregoing figures, the exposed substrate is coloured black in FIG. 6A.

[0093] In FIG. 6B, a first layer of superconducting material 631 is deposited onto the workpiece 600 using angular evaporation from a first direction. The first layer of superconducting material 631 is deposited onto the workpiece 600 partially into the first recess 602a, 602a, 602b, 602c and 602d, and into the elongated trenches 603a, 603c, and 603e. Because of the layer of resist material 608 casts 'shadows', not the entire substrate within the 602a, 602a, 602b, 602c and 602d is covered by superconducting material and no superconducting material is deposited into elongated trenches 603b, and 603d.

[0094] In FIG. 6C, a second layer of superconducting material 632 is deposited onto the workpiece600 using angular evaporation from a second direction, which is different from the aforementioned firstdirection. Again, because of the layer of resist material 608 casts 'shadows', there are areas within the etched pattern 601' in which no superconducting material is deposited. These areas include the elongated trenches 603a, 603c and 603e, which are coloured black in FIG. 6C.

[0095] FIG. 6D shows the workpiece 600 of the foregoing figures FIG. 6B and FIG. 6C having the first layer of superconducting material and the second layer of superconducting material. Within the recesses 602a, 602b, 602c and 602d, there are subareas 650a, 650b, 650c and 650d that in FIG. 6D are indicated by a diagonally dashed pattern partially outlined with a dotted line. In these subareas 650a, 650b, 650c and 65 Od, both the first layer of superconducting material and the second layer of superconducting material are present and overlap with one another. The subareas 650a, 650b, 650c and 650d are thus areas of overlap forming Josephson junctions.

[0096] From FIG. 6D, it can be discerned that these areas of overlap 650a, 650b, 650c, 65 Od differ from one another with respect to their surface area. Subarea 650c has a smaller surface area than subareas 650a and 650b, which in turn both have a smaller surface area than subarea 650d. It follows that the Josephson junctions constituted by these subareas 650a, 650b, 650d, 650d comprise correspondingly varying critical current, in spite of the initial recesses 602a, 602b, 602c, 602d in the layer of resist material 608 having identical dimensions.

[0097] The resulting respective surface areas of the areas of overlap 650a, 650b, 650c, 65 Od are, more adequately put, dependent on the orientations of the recesses 602a, 602b, 602c, 602d and the elongated trenches 603a, 603b, 603c, 603d, 603e relative to the angular evaporation disposition directions. This is considered problematic, because it significantly complicates a design process of a Josephson junction quantum mechanical device in which the critical currents of the various Josephson junctions should match specific predefined values.

[0098] FIG. 7A to FIG. 7D show subsequent steps of manufacturing a Josephson junction quantum mechanical device, in accordance with various alternative embodiments with which the abovedescribed limitation is overcome.

[0099] FIG. 7A shows a top-down view of a workpiece 700. The workpiece 700 comprises a substrate with a layer of resist material 708 arranged on atop surface of the substrate. A meandering pattern 701' has been etched into the layer of resist material 708, exposing the substrate underneath. The meanderingpatern 701' comprises recesses 702a, 702b, 702c and 702d, which in accordance with various embodiments may be approximately square. The recesses 702a, 702b, 702c and 702d are interconnected by elongated trenches 703a, 703b, 703c, 703d and 703e etched into the resist material 708. The exposed substrate is coloured black in FIG. 7A.

[0100] In contrast to the workpiece 600 of FIG. 6A to FIG. 6D, the elongated trenches 703a, 703b, 703c, 703d and 703e of the present workpiece 700 extend beyond the recesses 702a, 702b, 702c and 702d into free ends 704a, 704b, 705a, 705b, 706a, 706b, 707a and 707b. From FIG. 7A it can be discerned that the elongated trench 703b extends beyond recess 702a into a free end 704a and beyond recess 702b into free end 705b. Likewise, elongated trench 703c extends beyond recess 702b into free end 705a and beyond recess 702c into free end 706b. Moreover, the elongated trench 703d extends beyond recess 702c into free end 706a and beyond recess 702d into free end 707b.

[0101] Referring now to FIG. 7B, a first layer of superconducting material 731 is deposited onto the workpiece 700 using angular evaporation from a first direction. The first layer of superconducting material is deposited onto the workpiece 700 partially into the first recess 702a, 702a, 702b, 702c and 702d, and into the elongated trenches 703a, 703c, and 703e. Moreover, the superconducting material is deposited into the free ends 705a, 707a, and partially into 704b and 706b due to the layer of resist material 708 casting shadows. Also due to the casting of shadows, no superconducting material is deposited into the elongated trenches 703b and 703d, including free ends 704a, 705b, 706a and 707b.

[0102] In FIG. 7C, a second layer of a second layer of superconducting material 732, 732', is deposited onto the workpiece 700 using angular evaporation from a second direction, which is different from the aforementioned first direction. The second layer of superconducting material is deposited onto the workpiece 700 partially into the recesses 702a, 702b, 702c and 702d and into the elongated trench 703b (including free ends 704a and 705b) and the elongated trench 703d (including free ends 706a and 707b). No superconducting material is deposited into elongated trenches 703a, 703c 703e, nor in free ends 704b, 705a, 706b and 707a. Thereby the second layer of superconducting material 732, 732' is deposited into two separate regions 732, 732'.

[0103] FIG. 7D shows the workpiece 700 of the foregoing figures FIG. 7B and FIG. 7C having the first layer of superconducting material and the second layer of superconducting material. Within therecesses 702a, 702b, 702c and 702d, there are subareas 750a, 750b, 750c and 750d that in FIG. 7D are indicated by a diagonally dashed pattern partially outlined with a dotted line. In these subareas 650a, 750b, 750c and 75 Od, both the first layer of superconducting material and the second layer of superconducting material are present and overlap with one another. The subareas 750a, 750b, 750c and 650d are thus areas of overlap forming Josephson junctions.

[0104] From FIG. 7D, it can be discerned that these areas of overlap 750a, 750b, 750c, 750d are constant with respect to their surface area and therefore comprise substantially identical critical currents . In other words, the resulting respective surface areas of the areas of overlap 750a, 750b, 750c, 750d are independent from the orientations of the recesses 702a, 702b, 702c, 702d and the elongated trenches 703a, 703b, 703c, 703d, 703e relative to the angular evaporation disposition directions. This significantly simplifies the design and manufacturing of pluralities of Josephson junctions having specific, predefined areas of overlap and corresponding critical currents.

[0105] Since the area of overlap is constant, less critical current variation is obtained between Josephson junctions. This means that in an array with multiple Josephson junctions, e.g. placed in series and / or in a meandering pattern, the critical current variation between Josephson junctions will be minimal. Often, Josephson junctions that are placed in series need to be placed in a meandering pattern, which makes that the orientation of the Josephson junction varies. Using angular evaporation, one would geta a different area of overlap each time if not for the use of the free ends as described above, which makes that the area of overlap is substantially constant, and therefore also the critical current variation between the Josephson junctions, independent of the orientation of the Josephson junctions. A further benefit of this method is that it increases the tolerance for fabrication errors, since the free end forms an extra part with which it is possible to make electrical contact in case of misalignment. The method leads to an increase in yield.

[0106] FIG. 6A to FIG. 6D and FIG. 7A to FIG. 7D may relate to embodiments of Josephson junction quantum mechanical devices that comprise a chain of Josephson junctions, such as Josephson travelling wave parametric amplifiers (JTWPAs). JTWPAs may be used to perform signal processing, e.g. parametrically amplifying a signal to infer a quantum state of a superconducting qubit using dispersive readout. Nevertheless, similar advantages may be achieved with other types of Josephson junctionquantum mechanical devices that comprise multiple Josephson junctions, including Josephson junctions with constant or varying critical currents. These devices may include quantum processing units comprising multiple superconducting quantum bits with which quantum computations may be performed.

[0107] It will be appreciated that the skilled person may combine various features of the exemplary embodiments as described here above with reference to the appended drawing. The here abovedescribed embodiments should therefore not be construed as limiting the scope of the sought-after protection, which is defined solely by the features as defined in the appended claims and, at least in certain jurisdictions, their equivalents.

[0108] The following clauses are example embodiments of the invention.

[0109] 1. A Josephson junction quantum mechanical device (200), comprising: a first electrode (121) arranged on a substrate (401) and comprising a first elongated arm (221); a second electrode (122) arranged on the substrate (401) and comprising a second elongated arm (222), wherein the first elongated arm (221) and the second elongated arm (222) extend toward each other to define an area of overlap (250), wherein the first elongated arm (221) and the second elongated arm (222) each comprise, at the area of overlap (250), a respective first lateral flange (221 A, 222A), wherein the first lateral flange (221 A) of the first elongated arm (221) extends along a first lengthwise part (Pl) of the first elongated arm (221) and along a second lengthwise part (P2) of the second elongated arm (222); and the first lateral flange (222 A) of the second elongated arm (222) extends along a third lengthwise part (P3) of the second elongated arm (222) and along fourth lengthwise part (P4) of the first elongated arm (221), whereby the area of overlap (250) between the first electrode (121) and second elongated electrode is defined to comprise a surface area larger than a product of the respective widths of the first elongated arm (221) and second elongated arm (222).

[0110] 2. The Josephson junction quantum mechanical device (200) of clause 1, wherein at least one of the first electrode (121) and the second electrode ( 122) has been formed using an angular evaporation fabrication technique.

[0111] 3. The Josephson junction quantum mechanical device (200) of clause 1 or 2, wherein at least one of the first lateral flange (221 A) of the first elongated arm (221) and the first lateral flange (222A)of the second elongated arm (222) comprises a polygon shape, preferably a substantially rectangular shape.

[0112] 4. The Josephson junction quantum mechanical device (200) of anyone of the foregoing clauses, wherein the first lateral flange (222A) of the first or second elongated arm (222) protrudes in a direction non-parallel to a lengthwise direction of said first or second elongated arm (222).

[0113] 5. The Josephson junction quantum mechanical device (200) of any one of the foregoing clauses, wherein the first elongated arm (221) and the second elongated arm (222) each comprise, at the area of overlap (250), a respective second lateral flange (321B, 322B) opposite the first lateral flange.

[0114] 6. The Josephson junction quantum mechanical device (200) of clause 5, wherein the second lateral flange (32 IB) of the first elongated arm (221) extends along a fifth lengthwise part (P5) of the first elongated arm (221) and along a sixth lengthwise part (P6) of the second elongated arm (222), and the second lateral flange (322B) of the second elongated arm (222) extends along a seventh lengthwise part (P7) of the second elongated arm (222) and along an eighth lengthwise part (P8) of the first elongated arm (221).

[0115] 7. The Josephson junction quantum mechanical device (200) of any one of the foregoing clauses, wherein at least one, or both, of the first elongated arm (221) and the second elongated arm (222) comprises a respective free end (204a, 204b) that extends beyond the area of overlap (250) and beyond the first lateral flange of said first elongated arm (221) and / or second elongated arm (222).

[0116] 8. The Josephson junction quantum mechanical device (200) of any one of the foregoing clauses, wherein the first elongated arm (221) and the second elongated arm (222) are oriented relative to one another such that their respective lengthwise directions are non-parallel to one another.

[0117] 9. The Josephson junction quantum mechanical device (200) of any one of the foregoing clauses, wherein the first electrode (121) and the second electrode (122) form at least a portion of a superconducting qubit.

[0118] 10. The Josephson junction quantum mechanical device (200) of any one of the foregoing clauses 1 - 8, wherein the first electrode (121) and the second electrode (122) form at least a part of a transmission line of a Josephson travelling wave parametric amplifier, JTWPA.

[0119] 11. The Josephson junction quantum mechanical device (200) of any one of the foregoing clauses, wherein the substrate (401) comprises at least one of silicon, silicon dioxide, silicon nitride, sapphire, gallium arsenide, quartz, magnesium oxide, lithium niobate, lanthanum aluminate, strontium titanate, boron nitride, hafnium dioxide.

[0120] 12. The Josephson junction quantum mechanical device (200) of any one of the foregoing clauses, wherein at least one of the first and second electrodes (121,122) comprises at least one of aluminium, niobium, tantalum, lead, tin and molybdenum.

[0121] 13. A method of manufacturing a Josephson junction quantum mechanical device (200), the method comprising: providing a substrate (401) having a resist layer arranged thereon; patterning the resist layer to form, in the resist layer, a first elongated trench (441) and a second elongated trench (442), wherein the first elongated trench (441) and the second elongated trench (442) extend to intersect one another at an intersection (460); depositing a first layer of superconducting material (431) on the patterned resist layer (408); and depositing a second layer of superconducting material on the patterned resist layer (408) wherein patterning the resist layer comprises: forming, at the intersection (460) between the first and second trenches (441, 442), a first recess (461) that extends laterally along a first part of the first elongated trench (441) and along a first part of the second elongated trench (442).

[0122] 14. The method of clause 13, wherein patterning the resist layer further comprises: forming, at the intersection (460) between the first and second trenches, a second recess (562) opposite the first recess (461), wherein the second recess (562) extends laterally along a second part of the first elongated trench (441) and along a second part of the second elongated trench (442).

[0123] 15. The method of clause 13 or 14, wherein patterning the resist layer (408) further comprises: forming at least one, or both, of first elongated trench (441) and the second elongated trench (442) to comprise a free end that end that extends beyond the intersection (460) and beyond the first recess (461).

[0124] 16. The method of any one of the foregoing clauses 13 - 15, wherein at least one of depositing the first layer of superconducting material (431) and depositing the second layer of superconducting material (432), comprises usage of an angular evaporation fabrication technique.

[0125] 17. A method for performing a quantum computation, the method comprising usage of aJosephson junction quantum mechanical device (200) of any one of the foregoing clauses 1 - 12.

[0126] 18. A method for performing signal processing, the method comprising usage of a Josephson junction quantum mechanical device (200) of any one of the foregoing clauses 1 - 12.

Claims

CLAIMS1. A Josephson junction quantum mechanical device (200), comprising: a first electrode (211) arranged on a substrate (201) and comprising a first elongated arm (221); a second electrode (212) arranged on the substrate (201) and comprising a second elongated arm (222), wherein the first elongated arm (221) and the second elongated arm (222) extend toward each other to define an area of overlap (250), wherein the first elongated arm (221) and the second elongated arm (222) each comprise, at the area of overlap (250), a respective first lateral flange (221 A, 222A), wherein the first lateral flange (221 A) of the first elongated arm (221) extends along a first lengthwise part (Pi) of the first elongated arm (221) and along a second lengthwise part (P2) of the second elongated arm (222); and wherein the first lateral flange (222A) of the second elongated arm (222) extends along a third lengthwise part (P3) of the second elongated arm (222) and along fourth lengthwise part (P4) of the first elongated arm (221), whereby the area of overlap (250) between the first electrode (211) and second elongated electrode is defined to comprise a surface area larger than a product of the respective widths of the first elongated arm (221) and second elongated arm (222).

2. The Josephson junction quantum mechanical device (200) of claim 1, wherein at least one of the first electrode (211) and the second electrode (212) has been formed using an angular evaporation fabrication technique.

3. The Josephson junction quantum mechanical device (200) of claim 1 or 2, wherein at least one of the first lateral flange (221 A) of the first elongated arm (221) and the first lateral flange (222A) of the second elongated arm (222) comprises a polygon shape, preferably a substantially rectangular shape.

4. The Josephson junction quantum mechanical device (200) of anyone of the foregoing claims, wherein the first lateral flange (222A) of the first or second elongated arm (222) protrudes in a direction non-parallel to a lengthwise direction of said first or second elongated arm (222).

5. The Josephson junction quantum mechanical device (200) of any one of the foregoing claims, wherein the first elongated arm (221) and the second elongated arm (222) each comprise, at the area of overlap (250), a respective second lateral flange (32 IB, 322B) opposite the first lateral flange.

6. The Josephson junction quantum mechanical device (200) of claim 5, wherein the second lateral flange (32 IB) of the first elongated arm (221) extends along a fifth lengthwise part (Ps) of the first elongated arm (221) and along a sixth lengthwise part (Pe) of the second elongated arm (222), and the second lateral flange (322B) of the second elongated arm (222) extends along a seventh lengthwise part (P?) of the second elongated arm (222) and along an eighth lengthwise part (Ps) of the first elongated arm (221).

7. The Josephson junction quantum mechanical device (200) of any one of the foregoing claims, wherein at least one, or both, of the first elongated arm (221) and the second elongated arm (222) comprises a respective free end (204a, 204b) that extends beyond the area of overlap (250) and beyond the first lateral flange of said first elongated arm (221) and / or second elongated arm (222).

8. The Josephson junction quantum mechanical device (200) of any one of the foregoing claims, wherein the first elongated arm (221) and the second elongated arm (222) are oriented relative to one another such that their respective lengthwise directions are non-parallel to one another.

9. The Josephson junction quantum mechanical device (200) of any one of the foregoing claims, wherein the first electrode (211) and the second electrode (212) form at least a portion of a superconducting qubit.

10. The Josephson junction quantum mechanical device (200) of any one of the foregoing claims 1 - 8, wherein the first electrode (211) and the second electrode (212) form at least a part of a transmission line of a Josephson travelling wave parametric amplifier, JTWPA.

11. The Josephson junction quantum mechanical device (200) of any one of the foregoing claims, wherein the substrate (201) comprises at least one of silicon, silicon dioxide, silicon nitride, sapphire, gallium arsenide, quartz, magnesium oxide, lithium niobate, lanthanum aluminate, strontium titanate, boron nitride, hafnium dioxide.

12. The Josephson junction quantum mechanical device (200) of any one of the foregoing claims, wherein at least one of the first and second electrodes (211,212) comprises at least one of aluminium, niobium, tantalum, lead, tin and molybdenum.

13. A method of manufacturing a Josephson junction quantum mechanical device (200), the method comprising: providing a substrate (201) having a resist layer arranged thereon; patterning the resist layer to form, in the resist layer, a first elongated trench (441) and a second elongated trench (442), wherein the first elongated trench (441) and the second elongated trench (442) extend to intersect one another at an intersection (460); depositing a first layer of superconducting material (431) on the patterned resist layer (408); and depositing a second layer of superconducting material on the patterned resist layer (408) wherein patterning the resist layer comprises: forming, at the intersection (460) between the first and second trenches (441 , 442), a first recess(461) that extends laterally along a first part of the first elongated trench (441) and along a first part of the second elongated trench (442).

14. The method of claim 13, wherein patterning the resist layer further comprises:forming, at the intersection (460) between the first and second trenches, a second recess (562) opposite the first recess (461), wherein the second recess (562) extends laterally along a second part of the first elongated trench (441) and along a second part of the second elongated trench (442).

15. The method of claim 13 or 14, wherein patterning the resist layer (408) further comprises: forming at least one, or both, of first elongated trench (441) and the second elongated trench (442) to comprise a free end that end that extends beyond the intersection (460) and beyond the first recess (461).

16. The method of any one of the foregoing claims 13 - 15, wherein at least one of depositing the first layer of superconducting material (431) and depositing the second layer of superconducting material (432), comprises usage of an angular evaporation fabrication technique.

17. A method for performing a quantum computation, the method comprising usage of a Josephson junction quantum mechanical device (200) of any one of the foregoing claims 1 - 12.

18. A method for performing signal processing, the method comprising usage of a Josephson junction quantum mechanical device (200) of any one of the foregoing claims 1 - 12.

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