Device, apparatus, system and method for shifting the frequency of electromagnetic signals

Abstract

A device for shifting the frequency of electromagnetic signals, which comprises at least one integrated circuit formed on a substrate having at least one main side (3; 203; 303) provided with at least one first conductive layer (4; 204; 304) and at least one second conductive layer which are shaped to form interconnected electronic components comprising at least one signal port (7; 207; 307) configured to input into the device an electromagnetic signal at a frequency to be shifted and at least one modulation port (21; 221; 321) configured to input into the device a control signal for controlling the frequency shift of the electromagnetic signal in the device, wherein the second conductive layer comprises at least one waveguide (8; 208; 308) connected to the signal port (7; 207; 307), wherein the first conductive layer (4; 204; 304) and the second conductive layer comprise one or more strips (11, 12; 211, 212; 311, 312) coupled together so that a strip (11; 211; 311) of the second conductive layer at least partially covers a strip (12; 212; 312) of the first conductive layer (4; 204; 304), or vice versa, wherein at least two overlapping portions of said strips (11, 12; 211, 212; 311, 312) coupled together and at least one dielectric layer which is disposed between these two overlapping portions form a Josephson junction (6; 206; 306). The present description also relates to an apparatus and a system comprising such a device and a method which can be implemented by such a device, such an apparatus and / or such a system.

Description

[0001] Device, apparatus, system and method for shifting the frequency of electromagnetic signals

[0002] Technical field

[0003] The present description relates to a device for shifting the frequency of electromagnetic signals, particularly electromagnetic pulses, such as photon pulses or microwave pulses. The present description also relates to an apparatus and a system comprising such a device and a method that can be implemented by such a device, apparatus, and / or system.

[0004] Background of the description

[0005] Known methods and devices for shifting the frequency of electromagnetic signals are used in a wide range of electronic and communications systems to enable the efficient transmission, reception, and processing of electromagnetic signals across different frequency bands. Common known methods include mixing, heterodyning, and direct digital synthesis.

[0006] Radio frequency and microwave mixers are essential components in a wide range of electronic systems. These devices are used to shift the frequency of electromagnetic signals in a method known as frequency mixing, particularly in applications such as communications systems, radar, and signal processing. A mixer typically combines two signals: the input electromagnetic signal, particularly a radio frequency (RF) signal, and a local oscillator control signal. The mixer outputs signals based on the sum and difference of the input frequencies, allowing the conversion of high-frequency signals to lower frequencies (downconversion) or the generation of higher-frequency signals from lower frequencies (upconversion). This frequency shifting simplifies signal processing, filtering, and amplification, which are more efficient at lower frequencies. In communications systems, mixers enable the transmission and reception of signals across various frequency bands. For example, in a radio receiver, a mixer converts the received electromagnetic signals into an intermediate frequency, making signal amplification and processing easier. Similarly, in radar systems, mixers play a key role in generating the necessary high-frequency signals and converting the received signals for their analysis. Mixers come in various configurations, including diode mixers, FET mixers, microwave mixers, and balanced mixers, each with its own set of characteristics and performance tradeoffs, and are used in numerous applications beyond communications, including instrumentation, test and measurement, and scientific research. Despite their widespread use and importance, radio frequency and microwave mixers have several limitations when applied to cutting-edge technologies such as quantum computing. One disadvantage of known mixers is their relatively large size, making them difficult to integrate into compact systems. Furthermore, known mixers generally require high- power carriers, which can introduce significant power consumption and heat dissipation issues.

[0007] Moreover, radio frequency and microwave mixers are not inherently compatible with the cryogenic temperatures required for quantum computing, as superconducting quantum computers operate at temperatures on the order of milliKelvin (mK) to maintain qubit coherence and minimize thermal noise. Traditional mixers therefore cannot be used at temperatures near absolute zero, as their high power requirements and thus the heat they generate can disrupt the delicate cryogenic environment of quantum computers.

[0008] Summary of the description

[0009] The object of the present description is therefore to provide a device for shifting the frequency of electromagnetic signals that solves these problems. This object is achieved with a device, an apparatus, a system, and a method, the main features of which are specified in the appended claims, which are to be considered an integral part of the present description.

[0010] Due to their characteristics, the device, apparatus, system, and method according to the present description enable relatively efficient frequency switching of electromagnetic signals, particularly for linear frequency conversion of microwave pulses within superconducting circuits. While traditional microwave frequency conversion relies on nonlinear mixing methods, which can introduce unwanted harmonics and noise, the method according to the present description employs a linear, amplitude-tunable approach to achieve frequency conversion, preferably carried out by means of the device according to the present description. This method provides precise frequency control and is particularly advantageous for applications in quantum computing and quantum sensing. In particular, the device according to the present description comprises a linear frequency variator that can receive an electromagnetic signal and emit it at a controlled frequency, thanks to various embodiments of the device that can be selected depending on the application requirements.

[0011] Some embodiments of the device comprise a frequency-tunable cavity, particularly implemented as a superconducting microwave resonator on an integrated circuit comprising Josephson junctions.

[0012] Other embodiments of the device comprise a variable length electrical transmission line, in particular a superconducting waveguide incorporating a series of Josephson junctions.

[0013] The device can shift the frequency of a signal that is then transmitted to a specific application, for example the operation or control of a resonant object like a resonator or a qubit. The pulse shape of the signal can be designed to suit its intended use or to compensate for distortions typically caused by resonant devices.

[0014] To achieve the frequency shift, the device can receive a control signal, in particular a modulation pulse, to shift the frequency of the electromagnetic signal by altering the refractive index of the transmission line or cavity.

[0015] For effective transmission line-based frequency shifting, the propagation velocity of the control signal is preferably larger than the propagation velocity of the electromagnetic signal, while for effective cavity-based frequency shifting, the duration of the wavefront ramp of the control signal is preferably smaller than the ring-up time of the resonator.

[0016] The method according to the present description may comprise the generation of an electromagnetic signal intended to shift frequency, the generation of a control signal that changes the properties of the electromagnetic signal as it passes, for example, through the device according to the present disclosure, and the control of the frequency of the electromagnetic signal output from the device by tuning the amplitude of the control signal.

[0017] The electromagnetic signal and the control signal can be generated by using intermediate frequency digitizers, converted through a local oscillator or through highspeed fully digital electronics. The frequency-tunable cavity-based device is preferably operated in reflection by using a circulator, so that a single signal port can serve as both the input and output port of the device.

[0018] The aforementioned frequency-shifting techniques thus offer a linear and tunable solution that is particularly suitable for integration into systems comprising superconducting circuits. Precise control over electromagnetic signal frequencies, particularly microwave pulses, and compatibility with quantum technologies make the device, apparatus, system, and method according to the present description a valuable tool for future quantum computing and sensing applications.

[0019] Furthermore, the device is compact, consumes relatively little electrical power, and can be easily used in systems operating at temperatures close to absolute zero.

[0020] Brief description of the drawings

[0021] Further advantages and features of the device, apparatus, system and method according to the present description will become apparent to those skilled in the art from the following detailed description of some embodiments, to be considered as non-limiting examples of the claims, with reference to the attached drawings in which: figure 1 is an axonometric view of a first embodiment of the device; figure 2 is the enlarged detail II of figure 1 ; figure 3 is a top view of the device of figure 1 ; figure 4 is the enlarged detail IV of figure 3; figure 5 is the enlarged detail V of figure 3; figure 6 is section VI-VI of figure 4; figure 7 is section VII-VII of figure 4; figure 8 is section VIII-VIII of figure 5; figure 9 is section XI-XI of figure 5; figure 10 is section XX of figure 5; figure 11 is a first axonometric top view of an embodiment of the apparatus without cover; figure 12 is a second axonometric top view of the apparatus of figure 11 ; figure 13 is a top view of the apparatus of figure 11 ; figure 14 is section XIV-XIV of figure 13; figure 15 is section XV-XV of figure 13; figure 16 is a side view of the apparatus of figure 11 ; figure 17 is a front view of the apparatus of figure 11 ; figure 18 is the axonometric view of the device of figure 11 with cover; figure 19 is an axonometric view from below of the apparatus of figure 18; figure 20 is an exploded view of the apparatus of figure 18; figure 21 is a top view of a support of the apparatus of figure 18; figure 22 shows some steps of the manufacturing of the device of figure 1 ; figure 23 is a scheme of an embodiment of the system; figure 24 is a first diagram of an embodiment of the method; figure 25 is a second diagram of an embodiment of the method; figure 26 is a top view of a second embodiment of the device; figure 27 is the enlarged detail XXVII of figure 26; figure 28 is the enlarged detail XXVIII of figure 27; figure 29 is a top view of a third embodiment of the device; figure 30 is the enlarged detail XXX of figure 29; figure 31 is the enlarged detail XXXI of figure 29; figure 32 is the enlarged detail XXXII of figure 29.

[0022] Exemplary embodiments

[0023] Figures 1-10 show a first embodiment of the device 1 , which comprises at least one integrated circuit formed on a substrate 2, for example a silicon chip, which has at least one main side 3 (upper in the figures) provided with at least two conductive layers, i.e. layers formed from conductive material, in particular aluminum, which are shaped to form interconnected electronic components on the main side 3 of the substrate 2. In particular, the conductive layers are made from superconductive material, so that the conductive layers become superconductive below a critical temperature.

[0024] The substrate 2 preferably has a substantially parallelepiped shape, with a length L of 8- 12 mm, in particular about 10 mm, a width W of 2-6 mm, in particular about 4 mm, and / or a thickness T of 0.3-0.7 mm, in particular about 0.5 mm.

[0025] The substrate 2 comprises a first conductive layer 4 which is arranged on the main side 3, preferably covering it in a substantially uniform and / or complete manner. The first conductive layer 4 is preferably provided with a matrix of dots 5 in which the conductive layer 4 is not present, so that the main side 3 of the substrate 2 is exposed at these dots 5.

[0026] The first conductive layer 4 is coupled with a second conductive layer, still arranged on the main side 3, to form one or more Josephson junctions 6.

[0027] The second conductive layer comprises at least one signal port 7, in particular comprising at least one pad, and at least one waveguide 8 connected to the signal port 7. The signal port 7 is connected through the waveguide 8 to a shaped portion 9 of the second conductive layer. The waveguide 8 preferably has an elongated shape, in particular a substantially rectangular shape.

[0028] The signal port 7 is configured to input electromagnetic signals at a frequency to be shifted into the waveguide 8 and, preferably, also output said electromagnetic signals at a shifted frequency into the device 1.

[0029] The signal port 7, the waveguide 8 and / or the shaped portion 9 of the second conductive layer are separated from the first conductive layer 4, except at the Josephson junctions 6, by one or more channels 10 in which the main side 3 of the substrate 2 is exposed.

[0030] The pad of the signal port 7 has a substantially pentagonal shape with a substantially rectangular portion connected to a substantially triangular portion having a vertex connected to one end of the waveguide 8, so that the signal port 7 is tapered toward the waveguide 8. Therefore, the width of the pad, preferably 120-180 pm, particularly about 150 pm, gradually decreases toward the width, preferably 8-12 pm, particularly about 10 pm, of the waveguide 8. The tapered shape of the signal port 7 gradually adapts the impedance of the waveguide 8, particularly about 50 Ohms, to dimensions compatible with those of typical superconducting quantum circuit components, i.e. , dimensions on the order of microns.

[0031] The thickness, preferably 60-100 nm, particularly about 80 nm, of the first conductive layer 4 is less than the thickness, preferably 140-180 nm, particularly about 160 nm, of the second conductive layer. In figures 6-10, the thicknesses of the conductive layers are not shown to scale.

[0032] The shaped portion 9 of the second conductive layer in turn comprises one or more strips 11 coupled with one or more strips 12 of the first conductive layer 4, so that a strip 11 of the second conductive layer at least partially covers a strip 12 of the first conductive layer 4, or vice versa, i.e. a strip 12 of the first conductive layer 4 can at least partially cover a strip 11 of the second conductive layer. A Josephson junction 6 comprises the overlapping portions of a strip 11 of the second conductive layer and a strip 12 of the first conductive layer 4, as well as a dielectric layer 13, in particular made of aluminum oxide, which is arranged between the two overlapping portions of the strips 11 , 12.

[0033] Preferably, at least one strip 11 , in particular each strip 11 , of the second conductive layer is substantially parallel to the longitudinal axis K of the waveguide 8 and / or is substantially perpendicular to the strip 12 of the first conductive layer 4 coupled with the strip 11 of the second conductive layer. The maximum width, preferably 40-55 pm, in particular about 46 pm, of the shaped portion 9 of the second conductive layer is preferably greater than the width of the waveguide 8. The width S, preferably 2-4 pm, of a strip 11 of the second conductive layer is substantially equal to the width of the strip 12 of the first conductive layer 4 coupled with the strip 11 of the second conductive layer. In particular, the width of the strips 11 of the second conductive layer and / or of the strips 12 of the first conductive layer 4 is about 3 pm, so that a Josephson junction 6 occupies a surface area of about 9 pm2. The critical current of a Josephson junction 6 is about 2 pA.

[0034] The first conductive layer 4 may comprise a substantially T-shaped extension 14, in which two coaxial sections, i.e. the horizontal sections of the T, form the strips 12 of the first conductive layer 4. The shaped portion 9 of the second conductive layer may comprise a substantially T-shaped extension 15, in which the strips 11 of the second conductive layer are connected to two coaxial sections, i.e., the horizontal sections of the T, at their respective ends. The coaxial sections of the extensions 14, 15 of the first conductive layer 4 and of the second conductive layer are substantially parallel to each other. Preferably, the signal port 7, the shaped portion 9 of the second conductive layer, the channels 10 and / or the extension 14 of the first conductive layer 4 are substantially symmetrical with respect to the longitudinal axis K of the waveguide 8.

[0035] The waveguide 8 preferably comprises at least one capacitive portion 16 formed by at least one gap 17 in the waveguide 8. The gap 17 in turn comprises a longitudinal portion connected to two transverse portions, so that the capacitive portion 16 comprises two capacitive strips 18, 19 which are substantially parallel to each other and are electrically separated by the gap 17, so that the capacitive strips 18, 19, which act as plates, and the gap 17, which acts as a dielectric, act as a decoupling capacitor of the device 1.

[0036] The waveguide 8 preferably comprises at least one resonant portion 20, in particular formed by the portion of the waveguide 8 arranged between the capacitive portion 16 and the shaped portion 9 of the second conductive layer. The resonant portion 20 of the waveguide 8 is configured to resonate an electromagnetic signal transmitted into the waveguide 8.

[0037] The first conductive layer 4 may comprise a modulation port 21 , in particular comprising at least one pad, which is connected through at least one modulation line 22 to an inductive portion 23 which is arranged adjacent to the Josephson junctions 6. The modulation port 21 and the modulation line 22 are separated from the first conductive layer 4 by one or more channels 24, in which the main side 3 of the substrate 2 is exposed. The end 25 of the inductive portion 23 opposite the modulation port 21 is electrically connected to the remainder of the first conductive layer 4, which may in turn be connected to ground, in which case the inductive portion 23 may be used as a flux bias inductor for the resonant portion 20, as will be explained later.

[0038] The pad of the modulation port 21 has a substantially pentagonal shape with a substantially rectangular portion connected to a substantially triangular portion having a vertex connected to one end of the modulation line 22, so that the modulation port 21 is tapered toward the modulation line 22. Therefore, the width of the pad, preferably 120- 180 pm, particularly about 150 pm, gradually decreases toward the width of the modulation line 21 , preferably 8-12 pm, particularly about 10 pm. The modulation line 21 preferably has an elongated shape, in particular comprising a substantially rectilinear portion connected to a curvilinear portion with three substantially quarter-circle-shaped bends, so that the inductive portion 23 of the modulation line 22 is substantially perpendicular to the waveguide 8. The waveguide 8 and the rectilinear portion of the modulation line 21 are preferably parallel, in particular coaxial with respect to the longitudinal axis K.

[0039] Preferably, the length A of the portion of the waveguide 8 between the signal port 7 and the capacitive portion 16 is 0.8-1.2 mm, in particular about 1 mm, the length B of the capacitive portion 16, i.e. of the gap 17 and the capacitive strips 18, 19, is 0.3-0.5 mm, in particular about 0.4 mm, the length C of the resonant portion 20 of the waveguide 8 is 4.5-5.1 mm, in particular about 4.8 mm, the width of the channel 10 next to the waveguide 8 is 4-8 pm, in particular about 6 pm, the maximum width of the channel 10 next to the shaped portion 9 is 25-30 pm, in particular about 27 pm, the width E of the capacitive strips 18, 19 is 3-4 pm, in particular about 3.5 pm, the width F of the gap 17 is 2.5-3.5 pm, in particular about 3 pm, the width G of the inductive portion 23 is 8-12 pm, in particular about 10 pm, the width H of the channels 24 is 4-8 pm, in particular about 6 pm, the length J of the straight portion of the modulation line 21 is 1.4-1 .6 mm, in particular about 1.5 mm, and / or the radius R of the loops of the curved portion of the modulation line 21 is 0.4-0.6 mm, in particular about 0.5 mm.

[0040] The resonant frequency fo=wo / 2TT of the resonant portion 20 of the waveguide 8 depends on its length C, i.e. on the distance between the capacitive portion 16 and the shaped portion 9. In the present embodiment, the resonant frequency fo is about 5 GHz.

[0041] The Josephson junctions 6 implement, if the device 1 is at a cryogenic temperature, at least one SQUID (Superconducting Quantum Interference Device) that terminates the resonant portion 20 towards ground, i.e. towards the first conductive layer 4. The Josephson junctions 6 comprised in the SQUID of the device 1 have their own inductance which therefore modifies the resonant frequency foot the resonant portion 20 by changing its electrical length. A magnetic flux passing through the area of the SQUID can vary the value of this added inductance and, consequently, the resonant frequency of the resonant portion 20. The device 1 therefore comprises a planar superconducting integrated circuit provided with a coplanar waveguide resonator terminated to ground through a SQUID.

[0042] For this purpose, the modulation line 22 connected to the modulation port 21 can function as a flux line that can pass a control signal from the modulation port 21 to ground, i.e. to the remainder of the first conductive layer 4 through the end 25 of the inductive portion 23, thereby allowing the control signal, preferably an electromagnetic signal, particularly a microwave pulse, combined with a direct current signal, to discharge to ground and thereby create a magnetic flux over the area of the SQUID. The wide bends in the curved portion of the modulation line 22 serve to change its direction gradually, as sharp bends would degrade the transmission of microwave control signals.

[0043] Figures 11-21 show an embodiment of the apparatus 30, which comprises the device 1 arranged in a seat 31 , in particular a recess of substantially parallelepiped shape, of a printed circuit board 32 provided with a plurality of conductive pads 34, 36, 38 arranged at least on one main side of a non-conductive substrate of the printed circuit board 32. In particular, the signal port 7 of the device 1 is connected, preferably through at least one jumper 33, to a conductive signal pad 34 of the printed circuit board 32 and / or the modulation port 21 of the device 1 is connected, preferably through at least one jumper 35, to a conductive modulation pad 36 of the printed circuit board 32. One or more portions of the first conductive layer 4 of the device 1 , in particular peripheral portions of the first conductive layer 4, are also connected, preferably through jumpers 37, to further conductive pads 38 of the printed circuit board 32. Jumpers 33, 35 and 37 preferably comprise aluminum wires soldered to the conductive pads 34, 36, 38 and to the first conductive layer 4 or to the pads of the ports 7 and 21 of the device 1 .

[0044] The printed circuit board 32 may comprise a plurality of openings 39, in particular circular holes, so that the shank of a screw 40 may be arranged in an opening 39 and the head (shown with a broken line in figure 21) of this screw 40 may come into contact with a portion of a conductive pad 38 electrically connected to an edge of the first conductive layer 4 of the device 1 , to ground it.

[0045] The printed circuit board 32 has a substantially rectangular shape, in particular substantially square, preferably with lobes 41 , in particular having a substantially semicircular shape, which protrude from one or more corners, in particular each corner, of the printed circuit board 32. The openings 39 are arranged in correspondence with the lobes 41 , so that the head of a screw 40 at least partially covers a lobe 41.

[0046] The shanks of the screws 40 which pass through the openings 39 of the printed circuit board 32 are screwed into threaded holes 42 made in a wall, in particular the bottom wall, of a cavity 43 of a container 44 which can be closed by a lid 45. For this purpose, the lid 45 is provided with openings 46, in particular circular holes, so that the shank of a screw 47 can be placed in an opening 46 of the lid 45 and be screwed into a threaded hole 48 made in a wall 49, in particular the top wall, of the container 44 of the apparatus 30. The wall 49 of the container 44 facing the lid 45 can come into contact with the lid 45 when the screws 47 are screwed into the threaded holes 48, so as to cover the cavity 43 and close the container 44 with an electrical and thermal connection between the container 44 and the lid 45. In particular, two screws 47 are screwed into the container 44 and two screws 50, longer than the screws 47, are arranged in openings 46 in the lid 45, pass through through holes 51 made in the container 44 and protrude from a wall, in particular the lower wall, of the container 44, which is opposite the wall 49 facing the lid 45, so that the container 44, and therefore the entire apparatus 30, can be fixed to a support or other external element, in particular a plate of a refrigerator, with an electrical and thermal connection.

[0047] At least one connector, in particular two connectors 52, 53 for electromagnetic signals, more in particular two SMA (SubMiniature version A) connectors, is fixed to at least one side wall 54, in particular two opposite side walls, of the container 44 by means of one or more screws 55. The shaft of a screw 55 passes through a hole 56 made in a connector 52, 53 and is screwed into a threaded hole 57 made in the side wall 54 of the container 44. At least one connector 52, 53 is preferably arranged in a recess 58 made in a side wall 54 of the container 44.

[0048] At least one connector 52, 53 comprises a pin 59 that passes through an opening 60, in particular a circular hole, made in a side wall 54 of the container 44 and is electrically connected, in particular soldered, to the conductive pad 34 or 36 of the integrated circuit 32, before the container 44 is closed by means of the lid 45. A portion of the pin 59 arranged in an opening 60 is preferably covered by a layer 61 of insulating material. In particular, a first connector 52 is connected through the conductive signal pad 34 of the integrated circuit 32 to the signal port 7 of the device 1 and a second connector 53 is connected through the conductive modulation pad 36 of the integrated circuit 32 to the modulation port of the device 1 .

[0049] Thus, an electromagnetic signal, in particular a microwave pulse, at a frequency to be shifted in the device 1 and a control signal for controlling the frequency shift of said electromagnetic signal in the device 1 can be transmitted respectively to the signal port 7 and the modulation port 21 of the device 1 through electrical cables (not shown in the figures) provided with complementary connectors which are connected to the connectors 52, 53 of the apparatus 30.

[0050] The cavity 43 of the container 44 has a substantially prism shape, in particular with a base, i.e. the bottom wall, having a profile substantially equal to the profile of the integrated circuit 32. The container 44 and / or the lid 45 have a substantially prism shape, in particular with a base having a substantially octagonal profile. The recesses 58 of the container 44 have a substantially prism shape, in particular with a base, i.e. a portion of a wall 54 of the container 44, having a substantially rectangular profile. The container 44, the lid 45, and / or the screws 40, 47, 50, and / or 55 are made of an electrically and thermally conductive material that is resistant to cryogenic temperatures. Preferably, the container 44 and / or the lid 45 are made of copper. The container 44, the lid 45, and / or the screws 40, 47, 50, and / or 55 of the apparatus 30 form an enclosure that can be grounded through the same ground plate of the cooler used to cool the apparatus 30 and thus the device 1 to cryogenic temperatures, particularly temperatures below 1 K.

[0051] Preferably, the container 44 with the lid 45 of the apparatus 30 occupies a volume of less than 400 mm3, in particular 100-200 mm3, more particularly about 150 mm3, has a height of 15-20 mm, in particular about 17 mm, has a depth of 25-35 mm, in particular about 30 mm, and / or has a width of 25-35 mm, in particular about 30 mm.

[0052] Figures 22a-22h show schematically some steps of the manufacturing process of device 1.

[0053] In a first step, shown in figure 22a, a first uniform layer 70 of conductive material, in particular aluminium, is applied to the main side 3 of the substrate 2 of the device 1 , preferably by sputtering of metal particles 71, in particular aluminium particles.

[0054] In a second step, shown in figure 22b, a first mask 72 is applied to the first uniform layer 70, preferably by photolithography. The first mask 72 forms a pattern substantially equal to the final shape of the first conductive layer 4 of the device 1. In particular, the strip shown in figure 22b corresponds to a portion of a strip 12 of the first conductive layer 4 of the device 1.

[0055] In a third step, shown in figure 22c, portions of the first uniform layer 70 that are not covered by the first mask 72 are removed from the main side 3 of the substrate 2, preferably by chemical etching, in particular with an acid 73, so as to leave on the main side 3 of the substrate 2 the first conductive layer 4 of the device 1 in its final form.

[0056] In a fourth step, shown in figure 22d, the first mask 72 is removed, for example by a solvent 74, and the exposed surface of the first conductive layer 4 of the device 1 is oxidized, in particular by exposure to an oxidizing gas, for example air or oxygen.

[0057] In a fifth step, shown in figure 22e, a second mask is applied to the main side 3 of the substrate 2 or to the first conductive layer 4, where present, preferably by photolithography. The second mask preferably comprises at least two layers 75, 76, wherein the lower layer 76 facing the main side 3 of the substrate 2 is a layer of material known as “lift-off resist”, so as to form a small recess with respect to the upper layer 75 of the second mask. The second mask 75, 76 forms a pattern substantially negative of the final shape of the second conductive layer of the device 1. For example, the channel shown in figure 22e, where the second mask 75, 76 is not present, corresponds to a portion of a strip 11 of the second conductive layer of the device 1. The exposed surface of the first conductive layer 4 that is not covered by the second mask 75, 76 is removed, preferably by exposure to argon plasma 77, to remove the oxidized part of the first conductive layer 4.

[0058] In a sixth step, shown in figure 22f, the exposed surface of the first conductive layer 4, e.g. the exposed portion of the strip 12, is oxidized in a controlled manner, in particular by exposure to an oxidizing gas 78, e.g. air or oxygen, in a predefined quantity and for a predefined period of time, so as to obtain an oxidized layer, in particular aluminium oxide, having a predefined thickness, preferably 1-5 nm, in particular about 3 nm, on the exposed portion of the first conductive layer 4. In particular, said oxidized layer forms the dielectric layer 13 of a Josephson junction 6.

[0059] In a seventh step, shown in figure 22g, a second uniform layer 79 of conductive material, particularly aluminium, is applied to the second mask 75, 76 and, where this second mask 75, 76 is not present, to the main side 3 of the substrate 2 of the device 1 or to the exposed surface of the first conductive layer 4, preferably by sputtering of metal particles 80, in particular aluminium particles. In particular, the strip in the channel shown in figure 22b corresponds to a portion of a strip 11 of the second conductive layer of the device 1.

[0060] In an eighth step, shown in figure 22h, the second mask 75, 76 and portions of the second uniform layer 79 arranged above the second mask 75, 76 are removed, for example by means of a solvent, so as to expose the main side 3 of the substrate 2 and portions of the first conductive layer 4 and the second conductive layer of the device 1 formed on the main side 3 of the substrate 2, in particular the strips 11 , 12 which form a Josephson junction 6.

[0061] The method of manufacturing the device 1 may comprise further steps, performed before or after one or more of said eight steps, in which further conductive layers are applied on the main side 3 and / or on other sides of the substrate 2 to form further interconnected electronic components.

[0062] Figure 23 schematically shows an embodiment of the system 100, which comprises the device 1 , in particular arranged in the apparatus 30. The first conductive layer 4 of the device 1 is connected to ground through the conductive pads 38 of the printed circuit board 32, the screws 40, and the container 44 of the apparatus 30.

[0063] The system 100 preferably comprises a circulator 101 for using the signal port 7 of the device 1 as both an input port and an output port for shifting the frequency of an electromagnetic signal in the device 1. In particular, a first port (oriented downward in figure 23) of the circulator 101 is connected to the signal port 7 of the device 1 , preferably through the connector 52 of the apparatus 30, a second port (oriented to the right in figure 23) of the circulator 101 is connected to an input line 102 of the system 100, and a third port (oriented to the left in figure 23) of the circulator 101 is connected to an output line 103 of the system 100.

[0064] The system 100 preferably comprises a bias tee 104, i.e. a passive component configured to inject a direct current into a radio frequency circuit such as device 1 , which is connected to modulation port 21 of device 1 , preferably through connector 53 of device 30. Bias tee 104 is also connected to a high frequency line 105 and a direct current line 106 of system 100.

[0065] The system 100 thus comprises at least one input line 102 configured to transmit to the device 1 an electromagnetic signal with a frequency to be shifted, at least one output line 103 configured to receive from the device 1 the electromagnetic signal with the shifted frequency, and at least one control line, in particular comprising a high frequency line 105 and a direct current line 106, to transmit to the device a control signal for controlling the frequency of the electromagnetic signal in the device 1.

[0066] Preferably, the device 1 , the apparatus 30, the circulator 101 and / or the bias tee 104 are arranged in a metal housing 107, in particular made of copper and / or nickel-based alloy, e.g. Cryoperm® alloy, to protect the components arranged therein from external electromagnetic signals and / or magnetic fields.

[0067] The input line 102 of the system 100 preferably comprises a low-pass filter 108, one or more attenuators, in particular three attenuators 109, 110, 111 of about -30 dB, about - 40 dB and about -20 dB, respectively, for a total attenuation of about -90 dB, and / or a DC block 112 connected in series with each other. The DC block 112 is a component suitable for preventing the passage of direct current, if present in an alternating current signal.

[0068] The input line 102 of the system 100 is connected to a signal source 113, preferably through a switch 114 that allows the signal source 113 to be switched to a port of a network analyzer 115, in particular a vector network analyzer (VNA). The signal source 113 can emit an electromagnetic signal, in particular an electromagnetic pulse, for example a photon or microwave pulse, having a frequency to be shifted by the device 1 .

[0069] The output line 103 of the system 100 preferably comprises a low-pass filter 116, one or more isolators 117, 118, and / or one or more amplifiers 119, 120 connected in series with each other. In particular, the output line 103 comprises a first amplifier 119 with a gain of about +40 dB and a second amplifier 120 with a gain of about +36 dB. The first amplifier 119 and / or the second amplifier 120 are preferably high electron mobility field-effect transistor (HEMT) type amplifiers. The isolators 117, 118 prevent any noise generated by the amplifiers 119 and / or 120 from returning to the device 1.

[0070] Therefore, the electromagnetic signal to be processed in the device 1 to achieve a frequency shift is attenuated before it is processed by the device 1 and is amplified after it is processed by the device 1 .

[0071] The output line 103 of the system 100 is connected to a port of the network analyzer 115, preferably through a switch 121 which allows the network analyzer 115 to be switched with a device 122, in particular a quantum computer spectrum analyzer, which can use the electromagnetic signal emitted by the device 1.

[0072] The high frequency line 105 of the system 100 preferably comprises a low-pass filter 123, one or more attenuators, in particular two attenuators 124, 125 of about -20 dB and about -20 dB, respectively, for a total attenuation of about -40 dB, and / or a DC block 126 connected in series with each other.

[0073] The high frequency line 105 of the system 100 is connected to a control signal generator 127, in particular a variable frequency square wave signal generator. The direct current line 106 of the system 100 preferably comprises a low-pass filter 128 and is connected to a direct current source 129 configured to provide a bias current, preferably 5-15 mA, in particular about 10 mA, for one or more SQUIDs, if present in the device 1 .

[0074] The device 1 , the apparatus 30, the circulator 101, the bias tee 104, the metal housing 107, the low-pass filters 102, 116, 123, and / or 128, the isolators 117, 118, and / or the attenuator 109 may be arranged in a first cryogenic chamber 130, preferably at a temperature of 10-30 mK, in particular about 20 mK.

[0075] The attenuators 110 and / or 124 may be arranged in a second cryogenic chamber 131 , preferably at a temperature of 80-120 mK, in particular about 100 mK.

[0076] The first amplifier 119, the attenuator 111 and / or the attenuator 125 may be arranged in a third cryogenic chamber 132, preferably at a temperature of 3-5 K, in particular about 4 K.

[0077] One or more of said cryogenic chambers 130, 131 and / or 132 are preferably refrigerated by one or more stages of one or more dilution refrigerators.

[0078] The present system can be used in the following embodiment of the method for modifying the frequency of an electromagnetic signal.

[0079] For this purpose, the frequency and the amplitude of the control signal sent from the control signal generator 127 to the modulation port 21 of the device 1 defines the shift in frequency of the electromagnetic signal in the device 1 . The direct bias current generated by the direct current generator 129 sets the operating point of the SQUID and controls the range of variability of the resonant frequency of the resonant portion 20 as a function of the amplitude of the magnetic flux applied to the SQUID.

[0080] The diagram in figure 24 shows an example of correlation between the resonance frequency f=w / 2TT of the resonant portion 20 of the device 1 and the current Imod in the inductive portion 23 of the device 1 , which affects the amplitude of the magnetic flux applied to the SQUID, where the working point WP of the device 1 , in particular corresponding to a substantially zero magnetic flux (lmod=0), is set for example to about 4.43 GHz. The amplitude of the control signal, which affects the current Imod, can be adjusted in the control signal generator 127 as a function of the frequency shift that is desired to be obtained in the electromagnetic signal, in particular within a range of about 1 GHz.

[0081] As shown in figure 25, the frequency f1 of the electromagnetic signal sent to the signal port 7 of the device 1 and absorbed by the resonant portion 20 of the device 1 , which resonates at the resonant frequency f0, is modified to a frequency f=fo=wo / 2TT due to the resonance in the resonant portion 20, and then to a frequency f2=w / 2n=(wo+6w) / 2iTdue to the effect of the amplitude of the control signal on the resonant frequency of the resonant portion 20. The resonant portion 20 of the device 1 then shifts the frequency f1 of the electromagnetic signal, which is then retransmitted to the signal port 7 of the device 1 with a frequency f2.

[0082] Figures 26-28 show a second embodiment of device 201 , similar to the first embodiment of device 1 , but comprising multiple Josephson junctions connected in series to obtain a chain of SQUIDs, in particular ten SQUIDs, in which case the resonant frequency of the resonant portion depends more on the termination made by the SQUIDs, which therefore increasingly influence the frequency shift and allow the operating frequency range of device 201 to be expanded. Therefore, a single modulation line can simultaneously control the magnetic fluxes on all the SQUIDs in series, amplifying the effect in proportion to the number of SQUIDs present in device 201. This effect can be useful if the frequency shift generated by a device 201 with a single SQUID is not large enough for a given application.

[0083] As in the device 1 of the first embodiment, the device 201 comprises at least one integrated circuit formed on a substrate, e.g. a silicon chip, which has at least one main side 203 provided with at least one first conductive layer 204 which is arranged on the main side 203 and is preferably provided with a matrix of dots 205 in which the conductive layer 204 is not present, whereby the main side 203 of the substrate is exposed at these dots 205.

[0084] The device 201 also comprises a second conductive layer which is arranged on the main side 203, forms with the first conductive layer 204 a series of pairs of Josephson junctions 206 and comprises at least one signal port 207, a waveguide 208 and a shaped portion 209, wherein the signal port 207 is connected through the waveguide 208 to the shaped portion 209. The waveguide 208 preferably has an elongated shape, in particular a substantially rectangular shape, and comprises a bend, in particular with a quarter-circle shape, connected to the shaped portion 209.

[0085] The signal port 207, the waveguide 208, and / or the shaped portion 209 of the second conductive layer are separated from the first conductive layer 204, except at Josephson junctions 206, by one or more channels 210 where the main side 203 of the substrate is exposed.

[0086] The shaped portion 209 of the second conductive layer in turn comprises two strips 211 , each coupled with a strip 212 of the first conductive layer 204, such that a strip 211 of the second conductive layer partially covers a strip 212 of the first conductive layer 204, or vice versa. A Josephson junction 206 comprises the overlapping portions of a strip 211 of the second conductive layer and a strip 212 of the first conductive layer 204, as well as a dielectric layer that is disposed between the two overlapping portions of the strips 211 , 212.

[0087] To obtain a chain of SQUIDs connected in series, the strips 212 of the first conductive layer 204 are comprised in a first extension 214, substantially H-shaped, in which two coaxial sections of one of the two parallel segments, i.e. one of the two vertical segments of the H (which are however arranged horizontally in the figures), form the strips 212 of the first conductive layer 204, which are separated by the perpendicular segment, i.e. the horizontal segment of the H (which is however arranged vertically in the figures). Two further strips 212 of the first conductive layer 204 are connected to the second parallel segment of the H-shaped extension 214. Therefore, the first extension 214 and the two further strips 212 connected to the first extension 214 form a first conductive island of the first conductive layer 204, which comprises two first strips 212 substantially parallel to each other and two second strips 212 substantially perpendicular to the two first strips 212.

[0088] Each of the two second strips 212 connected to the first extension 214 of the first conductive island is coupled with a strip 211 of two further strips 211 of the second conductive layer to form a further pair of Josephson junctions 206. Said further strips 211 of the second conductive layer are comprised in a second extension 215, substantially H-shaped, in which two coaxial sections of one of the two parallel segments, i.e. of one of the two vertical segments of the H, form the two strips 211 of the second conductive layer, which are separated by the perpendicular segment, i.e. the horizontal segment of the H. Two further strips 211 of the second conductive layer are connected to the second parallel segment of the H-shaped extension 215. Therefore, the second extension 215 and the two further strips 211 connected to the second extension 215 form a first conductive island of the second conductive layer, which comprises two first strips 211 substantially parallel to each other and two second strips 211 substantially perpendicular to the first two strips 211.

[0089] Additional conductive islands with strips 211 , 212 coupled together to form Josephson junctions 206 may be connected in series in the manner described above to form a chain of SQUIDs connected in series one after the other.

[0090] The waveguide 208 preferably comprises at least one capacitive portion 216, in particular formed by at least one gap in the waveguide 208, as in the device 1 . The waveguide 208 comprises at least one resonant portion 220, in particular formed by the portion of the waveguide 208 disposed between the capacitive portion 216 and the shaped portion 209 of the second conductive layer.

[0091] The first conductive layer 204 comprises a modulation port 221 which is connected through at least one modulation line 222 to an inductive portion 223 which is disposed adjacent to the Josephson junctions 206 and comprises one end electrically connected to the rest of the first conductive layer 204. The modulation port 221 and the modulation line 222 are separated from the first conductive layer 204 by one or more channels 224, as in the device 1. The serially connected SQUIDs extend one after the other preferably along an axis M substantially perpendicular to the longitudinal axis K of the waveguide 20 and / or along a direction substantially parallel to the inductive portion 223. Preferably, the shaped portion 209 of the second conductive layer, the conductive islands of the first conductive layer 204 and / or the conductive islands of the second conductive layer of the device 201 are substantially symmetrical with respect to the axis M.

[0092] The dimensions of the electronic components of the second embodiment of the device 201 , as in the first embodiment of the device 1 , can vary depending on the characteristics of the electromagnetic signal to be processed and the required frequency shift. In the present second embodiment, the dimensions of the electronic components are substantially equal to the dimensions of the first embodiment of the device 1 , except for the length of the waveguide 208, which is longer due to its bend. Figures 29-32 show the device 301 according to a third embodiment, similar to the devices 1 and 201 according to the first two embodiments, since it comprises at least one integrated circuit formed on a substrate, for example a silicon chip, which has at least one main side 303 provided with at least one first conductive layer 304 which is arranged on the main side 303 and is preferably provided with a matrix of dots 305 in which the conductive layer 304 is not present, whereby the main side 303 of the substrate is exposed at these dots 305.

[0093] The device 301 also comprises a second conductive layer which is arranged on the main side 303, forms with the first conductive layer 304 a plurality of Josephson junctions 306 and comprises at least one signal port 307 and a waveguide 308. The device 301 also comprises a modulation port 321 , wherein the signal port 307 is connected through the waveguide 308 to the modulation port 321. The waveguide 308 preferably has an elongated shape.

[0094] The signal port 307, the waveguide 308, and the modulation port 321 are separated from the first conductive layer 304, except at the Josephson junctions 306, by one or more channels 310 in which the main side 303 of the substrate is exposed.

[0095] The waveguide 308 comprises a series of strips 311 of the second conductive layer and of strips 312 of the first conductive layer 304 alternating with each other, wherein the first strip 311 or 312 of the series is connected to the signal port 307 and the last strip 311 or 312 of the series is connected to the modulation port 321. Each strip 311 of the second conductive layer is coupled with a strip 312 of the first conductive layer 304, so that a strip 311 of the second conductive layer partially covers a strip 312 of the first conductive layer 304, or vice versa. A Josephson junction 306 comprises the overlapping portions of a strip 311 of the second conductive layer and a strip 312 of the first conductive layer 304, as well as a dielectric layer which is disposed between the two overlapping portions of the strips 311 , 312. Preferably, the strips 311 of the second conductive layer are substantially parallel to each other and substantially perpendicular to the strips 312 of the first conductive layer 304. In particular, the strips 311 of the second conductive layer form an angle of 40°-50°, in particular about 45° with the longitudinal axis K of the waveguide 308, so that the waveguide 308 has a substantially zigzag shape.

[0096] However, in this third embodiment the electromagnetic signal at the frequency to be modified is not stored in a resonator but travels through the waveguide 308 with properties that can be controlled by a control signal sent to the modulation port 321 , so that the waveguide 308 is a nonlinear waveguide.

[0097] The operating principle of this device 301 is, however, similar to that of the devices 1 and 201. In this third embodiment of the device 301, the frequency of the electromagnetic signal is shifted while it is traveling through the waveguide 308 from the signal port 307, and in particular it is shifted by a control signal, in particular an electromagnetic pulse, which travels from the modulation port 321 in the waveguide 308 in the opposite direction to the electromagnetic signal. The waveguide 308 preferably comprises 1000-2000 Josephson junctions 306, in particular about 1500 Josephson junctions 306 connected in series. As in the previous embodiments, the length of the waveguide 308 and the width of the channels 310 are determined based on the size of the Josephson junctions 306, in particular to have an impedance of 50 Ohms and to ensure that the propagation time of the signals in the waveguide 308 of the device 301 is sufficiently long. The size of the Josephson junctions 306 changes their inductance and hence the operating parameters of the device 301 , so the exact geometric dimensions of the Josephson junctions 306 and of the strips 311 , 312 depend on the specific embodiment of the waveguide 308. In this embodiment, the device 301 is simple since it essentially consists of a waveguide 308 comprising a series of Josephson junctions 306 from the signal port 307 to the modulation port 321. However, in alternative embodiments, the device 301 may comprise additional electronic components made by particular shapes of the first conductive layer 304, of the second conductive layer and / or of additional conductive layers.

[0098] In the present embodiment of the method, a control signal is transmitted to modulation port 321 to modify the frequency of an electromagnetic signal input through signal port 307. The control signal may also be a square wave of adjustable duration and amplitude as needed. The portion of waveguide 308 in which the control signal is present changes its properties, particularly its refractive index, so that if the electromagnetic signal and the control signal are superimposed in waveguide 308, the frequency of the electromagnetic signal depends on the amplitude of the control signal. In particular, the two signals are synchronized so that the control signal occupies a portion close to the modulation port 321 of the device 301 , while the electromagnetic signal passes through the waveguide 308, whereby the electromagnetic signal enters the waveguide 308 at a first frequency f1 and exits the modulation port 321 at a frequency f2 shifted as a function of the amplitude of the control signal. In this case, the output line 103 of the system 100 is connected to the modulation port 321 through a circulator. The dimensions of the electronic components of the third embodiment of the device 301 , as in the first two embodiments of the device 1 and 201 , can vary depending on the characteristics of the electromagnetic signal to be processed and the required frequency shift. Preferably, the width of the channel 310 is 20-22 pm, in particular about 21 pm, the width of the strips 311 , 312 is 4-6 pm, in particular about 5 pm, and / or the length of the strips 311 , 312 is 14-18 pm, in particular about 16 pm.

[0099] The devices 201 and 301 of the second and third embodiments may be combined with each other and / or with the device 1 of the first embodiment, may be arranged in the apparatus 30 and / or in the system 100 like the device 1 , and / or may be manufactured using the manufacturing method of the device 1.

[0100] Variations or additions may be made by those skilled in the art to the embodiments described and illustrated herein, while remaining within the scope of the following claims. In particular, further embodiments may include the technical features of one of the following claims with the addition of one or more technical features described in the text or illustrated in the drawings, taken individually or in any mutual combination, and comprising equivalent characteristics thereof.

[0101] Furthermore, terms used in the text and / or drawings are intended to be inclusive unless otherwise specified, so for example the terms “a”, “comprising”, “including a”, “having two”, or “provided with the” mean respectively “at least one”, “comprising, but not limited to”, “including at least one”, “having two or more”, or “provided with the at least one”.

[0102] The values cited in the text and / or shown in the drawings comprise a tolerance of at least 5%, unless otherwise specified.

Claims

Claims1. A device for shifting the frequency of electromagnetic signals, which comprises at least one integrated circuit formed on a substrate having at least one main side (3; 203; 303) provided with at least one first conductive layer (4; 204; 304) and at least one second conductive layer which are shaped to form interconnected electronic components comprising at least one signal port (7; 207; 307) configured to input into the device an electromagnetic signal at a frequency to be shifted and at least one modulation port (21 ; 221 ; 321) configured to input into the device a control signal for controlling the frequency shift of the electromagnetic signal in the device, characterised in that the second conductive layer comprises at least one waveguide (8; 208; 308) connected to the signal port (7; 207; 307), wherein the first conductive layer (4; 204; 304) and the second conductive layer comprise one or more strips (11 , 12; 211 , 212; 311 , 312) coupled together so that a strip (11 ; 211 ; 311) of the second conductive layer at least partially covers a strip (12; 212; 312) of the first conductive layer (4; 204; 304), or vice versa, wherein at least two overlapping portions of said strips (11 , 12; 211 , 212; 311 , 312) coupled together and at least one dielectric layer which is disposed between these two overlapping portions form a Josephson junction (6; 206; 306).

2. The device according to the preceding claim, wherein the signal port (7; 207) or the modulation port (312) is also configured to output said electromagnetic signal with a shifted frequency into the device.

3. The device according to one of the preceding claims, wherein the signal port (7; 207) is connected through the waveguide (8; 208) to a shaped portion (9; 209) comprising one or more strips (11 ; 211) of the second conductive layer.

4. The device according to the preceding claim, wherein the first conductive layer (4; 204) comprises an extension (14; 214), substantially T- or H-shaped, provided with two coaxial sections forming strips (12; 212) of the first conductive layer (4; 204), and / or wherein the shaped portion (9; 209) of the second conductive layer comprises an extension (15; 215), substantially T- or H-shaped, provided with two coaxial sections connected to strips (11 ; 211) of the second conductive layer.

5. The device according to one of the preceding claims, wherein an extension (214) of the first conductive layer (204) comprises at least two first strips (212) of the firstconductive layer (204) and is connected to at least two second strips (212) of the first conductive layer (204), wherein the two first strips (212) of the first conductive layer (204) are substantially parallel to each other and the two second strips (212) of the first conductive layer (204) are substantially perpendicular to the two first strips (212) of the first conductive layer (204), so as to form a conductive island of the first conductive layer (204) comprising the two first strips (212) and the two second strips (212) of the first conductive layer (204), and / or wherein an extension (215) of the second conductive layer comprises at least two first strips (211) of the second conductive layer and is connected to at least two second strips (211) of the second conductive layer, wherein the two first strips (211) of the second conductive layer are substantially parallel to each other and the two second strips (211) of the second conductive layer are substantially perpendicular to the two first strips (211) of the second conductive layer, so as to form a conductive island of the second conductive layer comprising the two first strips (211) and the two second strips(211) of the second conductive layer.

6. The device according to the preceding claim, wherein each of the two first strips(212) of a conductive island of the first conductive layer (204) is coupled with one of the two second strips (211) of a conductive island of the second conductive layer to form two Josephson junctions (206), and / or wherein each of the two first strips (211) of a conductive island of the second conductive layer is coupled with one of the two second strips (212) of a conductive island of the first conductive layer (204) to form two Josephson junctions (206).

7. The device according to one of the preceding claims, wherein the waveguide (8; 208) comprises at least one resonant portion (20; 220) configured to resonate an electromagnetic signal transmitted into the waveguide (8; 208).

8. The device according to the preceding claim, wherein the Josephson junctions (6; 206) implement, if the device is at a cryogenic temperature, at least one SQUID terminating the resonant portion (20; 220) towards the first conductive layer (4; 204).

9. The device according to one of the preceding claims, wherein the waveguide (8; 208) comprises at least one capacitive portion (16; 216) formed by at least one gap in the waveguide (8; 208).

10. The device according to one of the preceding claims, wherein the modulation port (21 ; 221) is connected through at least one modulation line (22; 222) to an inductive portion (23; 223) which is arranged adjacent to the Josephson junctions (6; 206), wherein the end of the inductive portion (23; 223) of the modulation line (22; 222) opposite the modulation port (21 ; 221) is electrically connected to the first conductive layer (4; 204).11 . The device according to one of the preceding claims, wherein the first conductive layer (4; 204) is connected to ground.

12. The device according to one of the preceding claims, wherein the signal port (7; 207; 307), the waveguide (8; 208; 308), the shaped portion (9; 209), the modulation port (21 ; 221 ; 321) and / or the modulation line (22; 222) are separated from the first conductive layer (4; 204; 304) by one or more channels (10, 24; 210, 224; 310) in which the main side (3; 203; 303) of the substrate is exposed.

13. The device according to one of the preceding claims, wherein the waveguide (308) comprises a series of strips (311) of the second conductive layer and strips (312) of the first conductive layer (304) alternating with each other.

14. The device according to the preceding claim, wherein the first strip of the series is connected to the signal port (307) and the last strip of the series is connected to the modulation port (321).

15. The device according to one of the preceding claims, wherein the waveguide (8; 208; 308) is substantially rectangular- or zigzag-shaped.

16. The device according to one of the preceding claims, wherein the thickness of the first conductive layer (4; 204; 304) is less than the thickness of the second conductive layer.

17. An apparatus for shifting the frequency of electromagnetic signals, which comprises at least one device according to one of the preceding claims and a printed circuit board (32), wherein the device is arranged in a recess (31) of the printed circuit board (32), wherein the printed circuit board (32) comprises a non- conductive substrate and a plurality of conductive pads (34, 36, 38) arranged at least on one main side of the substrate, wherein the signal port (7; 207; 307) of thedevice is connected to at least one conductive signal pad (34) of the printed circuit board (32) and / or the modulation port (21 ; 221 ; 321) of the device is connected to at least one conductive modulation pad (36) of the printed circuit board (32), wherein one or more portions of the first conductive layer (4; 204; 304) of the device are connected to further conductive pads (38) of the printed circuit board (32).

18. The apparatus according to the preceding claim, which also comprises a container (44) and a lid (45) which are made of electrically and thermally conductive material and resistant to cryogenic temperatures, wherein the printed circuit board (32) with the device is arranged in a cavity (43) of the container (44) closed by the lid (45).

19. The apparatus according to the preceding claim, wherein at least one connector (52, 53) for electromagnetic signals is fixed to at least one wall (54) of the container (44) and comprises a pin (59) which passes through an opening (60) made in this wall (54) and which is electrically connected to a conductive signal pad (34) or to the conductive modulation pad (36) of the integrated circuit (32).

20. A system for shifting the frequency of electromagnetic signals, which comprises at least one device or apparatus according to one of the preceding claims, at least one input line (102) configured to transmit to the device the electromagnetic signal with a frequency to be shifted, at least one output line (103) configured to receive from the device the electromagnetic signal with the shifted frequency, and at least one control line (105, 106) for transmitting to the device the control signal for controlling the frequency shift of the electromagnetic signal in the device.

21. The system according to the preceding claim, which also comprises at least one circulator (101), wherein a first port of the circulator (101) is connected to the signal port (7; 207; 307) of the device, a second port of the circulator (101) is connected to the input line (102) and a third port of the circulator (101) is connected to the output line (103).

22. The system according to claim 20 or 21 , wherein the control line (105, 106) comprises a high frequency line (105) and a direct current line (106).

23. The system according to the preceding claim, which also comprises at least one bias tee (104) which is connected to the modulation port (21 ; 221 ; 321) of the device, to the high frequency line (105) and to the direct current line (106).

24. The system according to one of claims 20 to 23, wherein the device, the apparatus, the circulator (101) and / or the bias tee (104) are arranged in a metal housing (107).

25. The system according to one of claims 20 to 24, wherein the input line (102) comprises a low-pass filter (108), one or more attenuators (109, 110, 111) and / or a DC block (112) connected in series with each other.

26. The system according to one of claims 20 to 25, wherein the output line (103) comprises a low-pass filter (116), one or more isolators (117, 118) and / or one or more amplifiers (119, 120) connected in series with each other.

27. The system according to one of claims 22 to 26, wherein the high frequency line (105) is connected to a control signal generator (127) and comprises a low-pass filter (123), one or more attenuators (124, 125) and / or a DC block (126) connected in series with each other.

28. The system according to one of claims 20 to 27, wherein the device, the apparatus, the circulator (101), the bias tee (104), the metal housing (107), the low-pass filters (102, 116, 123, 128), the isolators (117, 118), the attenuators (109, 110, 111 , 124, 125) and / or at least one (119) of said amplifiers (119, 120) are arranged in one or more cryogenic chambers (130, 131 , 132).

29. A method of shifting the frequency of electromagnetic signals, wherein an electromagnetic signal at a frequency to be shifted is input through a signal port (7; 207; 307) into a waveguide (8; 208; 308) which is at a cryogenic temperature and which comprises or is connected to one or more Josephson junctions (6; 206; 306), wherein a control signal is input through a modulation port (21 ; 221 ; 321) into the waveguide (308) or into a modulation line (22; 222) coupled to the waveguide (8; 208), wherein the frequency of the electromagnetic signal is shifted at least as a function of the amplitude of the control signal.

30. The method according to the preceding claim, wherein the waveguide (8; 208) comprises a resonant portion (20; 220) and the electromagnetic signal input through the signal port (7; 207) is absorbed by the resonant portion (20; 220) of the waveguide (8; 208) and resonates in the resonant portion (20; 220) at a resonant frequency modified as a function of the amplitude of the control signal.

31. The method according to the preceding claim, wherein the waveguide (8; 208) is connected to at least one SQUID comprising one or more of said Josephson junctions (6; 206) and the modulation line (22; 222) comprises an inductive portion (23; 223) which generates on the SQUID a magnetic flux variable as a function of the amplitude of the control signal.

32. The method according to claim 29, wherein the amplitude of the control signal changes the refractive index of the waveguide (308).

33. The method according to one of claims 29 to 32, wherein the propagation speed of the control signal in the waveguide (8; 208; 308) is greater than the propagation speed of the electromagnetic signal in the waveguide (8; 208; 308).

34. The method according to one of claims 29 to 33, wherein the electromagnetic signal is attenuated before the frequency shift and is amplified after the frequency shift.

35. The method according to one of claims 29 to 34, wherein the method is implemented by the device according to one of claims 1 to 16, by the apparatus according to one of claims 17 to 19, or by the system according to one of claims 20 to 28.

36. A method for manufacturing the device according to one of claims 1 to 16, which comprises the following steps: a first uniform layer (70) of conductive material is applied on the main side (3; 203; 303) of the substrate of the device; a first mask (72) is applied over the first uniform layer (70), where the first mask (72) forms a pattern substantially equal to the final shape of the first conductive layer (4; 204; 304) of the device; portions of the first uniform layer (70) that are not covered by the first mask (72) are removed from the main side (3; 203; 303), so as to leave on the main side (3; 203; 303) the first conductive layer (4; 204; 304) of the device in its final form; the first mask (72) is removed; a second mask (75, 76) is applied on the main side (3; 203; 303) or on the first conductive layer (4; 204; 304), where present, where the second mask (75, 76) forms a pattern substantially negative with respect to the final shape of the second conductive layer of the device;the exposed surface of the first conductive layer (4; 204; 304) that is not covered by the second mask (75, 76) is removed; the exposed surface of the first conductive layer (4; 204; 304) which is not covered by the second mask (75, 76) is oxidized in a controlled manner to obtain an oxidized layer which forms the dielectric layer of a Josephson junction (6; 206; 306); a second uniform layer (79) of conductive material is applied on the second mask (75, 76) and, where this second mask (75, 76) is not present, on the main side (3; 203; 303) or on the exposed surface of the first conductive layer (4; 204; 304); the second mask (75, 76) and the portions of the second uniform layer (79) arranged above the second mask (75, 76) are removed.

37. The method according to the preceding claim, wherein the second mask (75, 76) comprises at least two layers (75, 76), wherein the lower layer (76) facing the main side (3; 203; 303) is a layer of “lift-off resist” material that forms a recess with respect to the upper layer (75) of the second mask (75, 76).

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