Radiofrequency circuit

Abstract

The invention relates to a radiofrequency circuit. Some exemplary embodiments relate to a displaced (i.e. spatially separated) low-reflection termination. Some exemplary embodiments relate to a radiofrequency waveguide structure, for example for controlling an intensity modulator or for a quantum computer. The radiofrequency circuit comprises a first circuit region, a second circuit region and a waveguide. The waveguide is designed to guide an alternating electromagnetic signal to an output coupling point at which a signal is output coupled from the waveguide, with the output coupling point being located in the second circuit region and the waveguide being designed to guide the alternating electromagnetic signal away from the output coupling point to a termination point at which the waveguide is terminated, wherein the termination point is located in the first circuit region such that a power loss that arises at the termination point is introduced into the first circuit region.

Description

[0001] High-frequency circuit

[0002] Description

[0003] Embodiments of the present invention relate to a radio-frequency circuit. Some embodiments relate to a dislocated (i.e., spatially separated) low-reflection termination. Some embodiments relate to a radio-frequency waveguide structure, for example, for driving an intensity modulator or for a quantum computer.

[0004] In high-frequency circuits (e.g. electronic systems) it is often the case that a high-frequency alternating quantity (e.g. voltage, current, power), for example with a precisely defined amplitude (or power), is required at a point in the circuit.

[0005] Conventionally, to generate an alternating voltage with a precisely defined amplitude, a high-frequency electromagnetic alternating signal is guided using a matched waveguide to the point in the circuit where the alternating voltage is required, as shown in Fig. 1.

[0006] In detail, Fig. 1 shows a schematic block diagram of a conventional circuit 10 in which a high-frequency electromagnetic alternating signal 16 generated by a signal source 14 is guided to point P of the circuit 10 by means of a waveguide 12, wherein the waveguide 12 is terminated via a load resistor 18. In other words, Fig. 1 shows a schematic representation of a high-frequency circuit. An electromagnetic alternating signal 16 is excited in the waveguide 12 by a signal source 14. The voltage required at point P in the circuit 10 is tapped off with a short line at the end of the waveguide 12. In order to avoid reflection of the electromagnetic wave at the end of the waveguide 12, the waveguide 12 is terminated at its end with a suitable load resistor 18.

[0007] Since wave propagation occurs on the waveguide 12 for transmitting the electromagnetic signal, and reflection would lead to the formation of a standing wave on the waveguide 12, the waveguide 12 is terminated at its end (e.g., via the load resistor 18) with the characteristic impedance of the line. The impedance of the matched waveguide lies within a range determined by technical constraints. The electrical power converted in the load resistor 18 is determined from the voltage value required at point P in the circuit 10 and the impedance of the waveguide.

[0008] A disadvantage of the described implementation is that the power converted in the load resistor 18 has a thermal effect near point P and may directly lead to a temperature increase in the circuit 10 or result in increased effort to dissipate heat from the circuit component. This is particularly problematic when stabilizing the temperature at a defined level is technically very complex, for example, when only very small temperature differences are permissible (e.g., adjacent circuit components only operate within a very small temperature range so that the required characteristics are maintained) or when the circuit components in question are at a temperature level at which only very low cooling capacity is available, for example, circuit components that operate at very low temperatures, which are achieved using a cryostat.

[0009] The present invention is therefore based on the object of creating a concept which makes it possible to reduce the effort required for the thermal stabilization of a circuit.

[0010] This problem is solved by the independent patent claims.

[0011] Advantageous further developments can be found in the dependent patent claims.

[0012] Embodiments provide a high-frequency circuit [e.g., high-frequency waveguide structure], having the following features: a first [e.g., two-dimensional or three-dimensional] circuit region, a second [e.g., two-dimensional or three-dimensional] circuit region, and a waveguide, wherein the waveguide is designed to guide an electromagnetic alternating signal to a coupling-out point at which a signal [e.g., alternating voltage, alternating current] is coupled out of the waveguide, wherein the coupling-out point is located in the second circuit region, wherein the waveguide is designed to guide the electromagnetic alternating signal away from the coupling-out point to a termination point at which the waveguide is terminated, wherein the termination point is located in the first circuit region, so that a power loss that occurs at the termination point [e.g., due to a termination of the waveguide] [e.g.,at least 80% or 90%] into the first circuit region.

[0013] In embodiments, the first circuit region may be defined by a first area or a first space that the first circuit region occupies or spans or encompasses.

[0014] In embodiments, the second circuit region may be defined by a second area or a second space that the second circuit region occupies or spans or encompasses.

[0015] In embodiments, heat generated by the power dissipation may be largely [e.g., at least 80% or 90%] applied to the first circuit region.

[0016] In embodiments, the first circuit region may be configured to operate at a first operating temperature, wherein the second circuit region may be configured to operate at a second operating temperature, wherein the second operating temperature is lower than the first operating temperature.

[0017] In embodiments, the first circuit region may be configured to operate within a first allowable operating temperature range, wherein the second circuit region may be configured to operate within a second allowable operating temperature range, wherein the second allowable operating temperature range is smaller than the first allowable operating temperature range.

[0018] In embodiments, significantly smaller [e.g., at least by a factor of 2, 3, 4, 5, or 10] temperature differences [e.g., around a first target temperature] may be permissible within the second temperature range than within the first temperature range.

[0019] In embodiments, a second operating temperature of the second operating temperature range may be lower than a first operating temperature of the first operating temperature range.

[0020] In embodiments, the first circuit region and the second circuit region can be thermally insulated from each other. In embodiments, a length of the waveguide between the coupling point and the termination point can be at least one-tenth of a wavelength of the alternating electromagnetic signal.

[0021] In embodiments, at least one electronic component arranged in the second circuit region can be supplied via the signal coupled out of the waveguide at the coupling-out point.

[0022] In embodiments, the signal can be coupled out at the coupling point via a coupling device.

[0023] In embodiments, the decoupling device may be configured to decouple the signal by means of a voltage tap, a power decoupling, a tap, a voltage divider, or a coupler.

[0024] In embodiments, the waveguide may be terminated at the termination point by a load resistance [e.g., line wave resistance].

[0025] In embodiments, the waveguide can serve as a terminating resistor.

[0026] In embodiments, the waveguide may have a coupling point at which the electromagnetic alternating signal is coupled into the waveguide.

[0027] In embodiments, the high-frequency circuit may include a signal source configured to generate the alternating electromagnetic signal.

[0028] In embodiments, the radio frequency circuit may comprise an intensity modulator, wherein the intensity modulator is arranged in the second circuit region, wherein the intensity modulator is supplied via the signal coupled out of the waveguide at the coupling-out point.

[0029] In embodiments, the waveguide may comprise a microstrip line or a coaxial cable.

[0030] Further embodiments provide a high-frequency circuit, having the following features: N circuit regions, where N is a natural number greater than or equal to two, N > 2, and M waveguides, where M is a natural number equal to N minus one, M = N-1 , where for a natural number i from one to N minus one, i = {1, N-1} an i-th waveguide of the M

[0031] Waveguide is designed to guide an i-th electromagnetic alternating signal to an i-th output point at which an i-th signal [e.g. alternating voltage, alternating current] is coupled out of the i-th waveguide, wherein the i-th output point lies in the (i+1)-th circuit region, and the i-th waveguide is designed to guide the i-th electromagnetic alternating signal away from the i-th output point to an i-th termination point at which the i-th waveguide is terminated, wherein the i-th termination point lies in one of an (i=1)-th to i-th circuit region of the N circuit regions, so that a power loss which arises at the i-th termination point [e.g. due to an i-th termination of the i-th waveguide] is introduced [e.g. at least 80% or 90%] into the circuit region in which the i-th termination point lies.

[0032] In embodiments, for a natural number k from two to N, k = {2, ... , N}, a k-th circuit region of the N circuit regions may be configured to operate at a k-th operating temperature, wherein the k-th operating temperature is less than a (k-1)-th operating temperature at which a (k-1)-th circuit region of the N circuit regions operates.

[0033] In embodiments, N can be a natural number greater than or equal to three, N > 3, where for a natural number i from one to N minus one, an (i+1)th coupling point of the (i+1)th waveguide and the i-th coupling point of the i-th waveguide are connected to one another via an i-th coupler located in the (i+1)th circuit region, the i-th coupler being designed to couple the i-th signal coupled out from the i-th waveguide into the (i+ 1)th waveguide as the (i+ 1)th electromagnetic alternating signal.

[0034] In embodiments, for a natural number k from two to N, a thermal noise of the k-th circuit region of the N circuit regions may be less than a thermal noise of the (k-1)-th circuit region.

[0035] In embodiments, for a natural number k from two to N minus one, a signal power and / or noise power from the (k-1)th circuit region to the (k+1)th circuit region may be attenuated by the coupling loss of the i-th coupler in the k-th circuit region.

[0036] In embodiments, at least one waveguide of the M waveguides may have a first waveguide section that runs between the coupling point of the respective waveguide and the coupling point of the respective waveguide, wherein the at least one waveguide may have a second waveguide section that runs between the coupling point of the respective waveguide and the termination point of the respective waveguide, wherein the second waveguide section has a higher attenuation or higher losses [e.g. poorer quality] than the first waveguide section.

[0037] In embodiments, the second waveguide section may comprise superconducting material.

[0038] In embodiments, the high-frequency circuit may comprise at least one cable, wherein the following features are integrated into the cable: the i-th coupling point of the i-th waveguide, the i-th coupler, the (i+1)-th coupling point of the (i+1)-th waveguide.

[0039] In embodiments, the i-th coupler may be implemented by means of a directional coupler.

[0040] In embodiments, the i-th coupler may be implemented using a power splitter and a directive element.

[0041] In embodiments, the high-frequency circuit may be a signal feed for a quantum computer.

[0042] Further embodiments provide a quantum computer having the following features: a laser signal source configured to generate a laser signal; a modulation signal source configured to generate an alternating electromagnetic signal; an intensity modulator configured to modulate an intensity of the laser signal based on the alternating electromagnetic signal; and a radio-frequency circuit according to any one of the embodiments described herein.

[0043] In embodiments, the second or N-th circuit region may be configured to operate at an operating temperature of 1 K or less.

[0044] In some embodiments, the laser signal source can be configured to generate a pulsed laser signal or a continuous wave laser signal as the laser signal. In some embodiments, the quantum computer can comprise multiple radio-frequency circuits for multiple qubits.

[0045] In embodiments, the quantum computer may comprise a radio frequency circuit according to any of the embodiments described herein, where N is a natural number greater than or equal to three, N > 3, where for a natural number k from two to N, k = {2, ... , N}, a k-th circuit region of the N circuit regions is configured to operate at a k-th operating temperature, where the k-th operating temperature is less than a (k-1)-th operating temperature at which a (k-1)-th circuit region of the N circuit regions operates.

[0046] Embodiments of the present invention are described in more detail with reference to the accompanying figures. They show:

[0047] Fig. 1 is a schematic block diagram of a conventional circuit in which a high-frequency electromagnetic alternating signal generated by a signal source is guided to a point of the circuit by means of a waveguide, the waveguide being terminated by a load resistor,

[0048] Fig. 2 is a schematic block diagram of a high-frequency circuit with two circuit regions, according to an embodiment of the present invention,

[0049] Fig. 3 is a schematic block diagram of a high-frequency circuit with two circuit regions, according to a further embodiment of the present invention,

[0050] Fig. 4 is a schematic block diagram of a high-frequency circuit with N = 3 circuit regions, according to an embodiment of the present invention,

[0051] Fig. 5 is a schematic block diagram of a high-frequency circuit with integrated intensity modulators for modulating optical laser signals and waveguides for supplying control signals for controlling the integrated intensity modulators, according to an embodiment of the present invention. Fig. 6 is a schematic block diagram of a conventional signal supply for a quantum computer for reducing thermal noise with attenuators at different temperature levels.

[0052] Fig. 7 is a schematic view of an attenuator with input noise power, attenuation and output noise power,

[0053] Fig. 8 schematic block diagram of a directional coupler in microstrip technology with input port, through port, coupled port and isolated port as well as the respective noise powers,

[0054] Fig.9 is a schematic block diagram of a high-frequency circuit with several circuit regions with different temperature levels for signal supply for a quantum computer, according to an embodiment of the present invention,

[0055] Fig. 10 is a schematic block diagram of a cable, wherein at least the i-th coupling point of the i-th waveguide, a directional coupler as the i-th coupler, and the (i+1)-th coupling point of the (i+1)-th waveguide are integrated in the cable, according to an embodiment of the present invention, and

[0056] Fig. 11 is a schematic block diagram of a cable, wherein at least the i-th coupling point of the i-th waveguide, a directive element and a power splitter as i-th coupler, and the (i+1)-th coupling point of the (i+1)-th waveguide are integrated in the cable, according to an embodiment of the present invention.

[0057] In the following description of the embodiments of the present invention, identical or equivalent elements in the figures are provided with the same reference numerals so that their description is interchangeable.

[0058] As already mentioned, in high-frequency circuits (e.g. electronic systems) it is often the case that a high-frequency alternating quantity (e.g. voltage, current, power), for example with a precisely defined amplitude (or power), is required at a point in the circuit. For example, to generate a defined alternating voltage, an electromagnetic alternating signal can be guided using a suitable waveguide to the point in the circuit where the voltage is required. At this point, the voltage is coupled out and the waveguide is conventionally terminated with low reflection (see introduction to the description above). The impedance of the waveguide is determined by technical boundary conditions. At the termination point, the energy carried by the electromagnetic alternating signal is converted into heat. The resulting thermal power loss may lead toThis means that increased effort is required to stabilize the temperature of the circuit part.

[0059] With the embodiments described below, the effort required for thermal stabilization of the circuit is (significantly) reduced.

[0060] Fig. 2 shows a schematic block diagram of a high-frequency circuit 100 (e.g., high-frequency waveguide structure) according to an embodiment of the present invention. The high-frequency circuit has a first circuit region 102i, a second circuit region 1022, and a waveguide 104. The waveguide 104 is designed to guide an alternating electromagnetic signal 106 to a coupling-out point P at which a signal 108, such as an alternating voltage or an alternating current, is coupled out of the waveguide 104, wherein the coupling-out point P lies in the second circuit region 1022. The waveguide 104 is designed to guide the alternating electromagnetic signal away from the coupling-out point P to a termination point 110 at which the waveguide 104 is terminated, wherein the termination point 110 lies in the first circuit region 102i, so that a power loss resulting from a termination of the waveguide 104 (e.g.,at least 80% or 90% is introduced into the first circuit region 1021.

[0061] This has the advantage that heat caused by the power loss resulting from the termination of the wave rider 104 is not introduced into the first circuit region (cf. Fig. 1), but into the second circuit region.

[0062] In embodiments, a length of the waveguide 104 between the coupling-out point P and the termination point 110 may be at least one-tenth of a wavelength of the alternating electromagnetic signal 106.

[0063] In embodiments, the waveguide 104 may be connected to a load resistor 112 (e.g.

[0064] line characteristic impedance), as shown by way of example in Fig. 2. Alternatively, the waveguide 104 itself can serve as the termination; for example, the part of the waveguide 104 between the coupling-out point P and the termination point 110 can serve as the termination.

[0065] In embodiments, the first circuit region 102i may be configured to operate at a first operating temperature (or first target temperature) Ti, wherein the second circuit region may be configured to operate at a second operating temperature (or second target temperature) T2, wherein the second operating temperature T2 is lower than the first operating temperature Ti, T2<Ti.

[0066] In embodiments, the first circuit region 102i may be configured to operate within a first allowable operating temperature range ATi (e.g., operating temperature range ATi between T1-AT1 / 2 and T1+AT1 / 2), wherein the second circuit region 1022 may be configured to operate within a second allowable operating temperature range AT2 (e.g., operating temperature range AT2 between T2-AT2 / 2 and T2+AT2 / 2), wherein the second allowable operating temperature range AT2 is smaller than the first allowable operating temperature range ATi, AT2<ATi.

[0067] In embodiments, significantly smaller (e.g., at least by a factor of 2, 3, 4, 5, or 10) temperature differences (e.g., around a first working temperature / target temperature) may be permissible within the second working temperature range AT2 than within the first working temperature range ATi, in which larger temperature differences (e.g., around a second working temperature / target temperature) may be permissible.

[0068] In embodiments, the first circuit region 102i and the second circuit region 1022 may be thermally isolated from each other.

[0069] In embodiments, at least one electrical or electronic component 114 arranged in the second circuit region 1022 can be supplied via the signal 108 coupled out of the waveguide 104 at the coupling-out point P, as indicated in Fig. 2. The electronic component 114 can be, for example, an intensity modulator (e.g., acousto-optical modulators or electro-optical modulators or deflectors). In embodiments, the signal 108 can be coupled out at the coupling-out point P via a coupling-out device, such as, for example, by means of a voltage tap, a power tap, a tap, a voltage divider, or a coupler.

[0070] In embodiments, the waveguide 104 may have a coupling point 116 at which the alternating electromagnetic signal 106 is coupled into the waveguide 104. The coupling point may be located at any point in the radio-frequency circuit, such as in the first circuit region 102i, as shown by way of example in Fig. 2.

[0071] In embodiments, the radio-frequency circuit 100 may further include a signal source 118 configured to generate the alternating electromagnetic signal 118. The signal source 118 may be located at any point in the radio-frequency circuit, such as in the first circuit region 102i, as shown by way of example in Fig. 2. In embodiments, the waveguide 104 may of course also be connected to an external signal source that is not part of the radio-frequency circuit 100.

[0072] The operation and further embodiments of the high-frequency circuit 100 shown in Fig. 2 are explained in more detail below with reference to Fig. 3.

[0073] Since the minimum power loss should be introduced at the point in the circuit where the electrical alternating voltage with a defined amplitude is required (point P in Fig. 3), the electromagnetic alternating signal is first guided to this point P using a waveguide. From point P, it is then guided to another location using another waveguide where no negative influence from the temperature increase is expected. At this location, remote from point P, the waveguide is terminated with a low-reflection resistor using a suitable load resistor.

[0074] Fig. 3 shows a schematic diagram illustrating the proposed approach with a dislocated low-reflection termination. A signal source 118 excites an alternating electromagnetic signal in the waveguide 104. The voltage required at point P in the circuit 100 is coupled out using a suitable device. The waveguide 104, which carries the alternating electromagnetic signal, is continued. The alternating electromagnetic signal is terminated at a location using the load resistor 112 where no negative impact from the introduced power loss is to be expected. In exemplary embodiments, the power loss does not occur at the location where the signal is required. This avoids negative influences on the circuit caused by heat.

[0075] In embodiments, there is a waveguide between the point in the circuit where the signal is required and the load resistor, on which wave propagation takes place (length of the waveguide > A / 10).

[0076] In embodiments, the coupling of the desired signal (e.g. voltage tap or power tap) can be carried out using a tap (e.g. direct contact or resistive contact), a voltage divider or a coupler (e.g. a directional coupler).

[0077] In the examples shown, the coupling-out structure is a structure that generates as little heat as possible.

[0078] In embodiments, the structure can be implemented once or multiple times.

[0079] In some embodiments, the waveguide itself can serve as a terminating resistor.

[0080] In the high-frequency circuit 100 shown in Figs. 2 and 3, it is assumed, by way of example, that the high-frequency circuit 100 has two circuit regions 102i and 1022. However, the invention is not limited to such embodiments.

[0081] Rather, the high-frequency circuit can be used. Embodiments N circuit regions 102i to 102 N where N is a natural number greater than or equal to two, N > 2. In embodiments, the radio frequency circuit may further comprise M waveguides 104i to 104M, where M is a natural number equal to N minus one, M = N-1.

[0082] Embodiments of a high-frequency circuit 100 with N = 2 circuit regions have already been discussed in detail above with reference to Figs. 2 and 3. The above explanations are also applicable in a corresponding manner to high-frequency circuits 100 with more than two circuit regions. Therefore, an embodiment of a high-frequency circuit 100 with N = 3 circuit regions is described below using Fig. 4 as an example. However, the following description is equally applicable to high-frequency circuits 100 with more than N = 3 circuit regions, i.e., N = 4 circuit regions, N = 5 circuit regions, N = 6 circuit regions, N = 7 circuit regions, N = 8 circuit regions, N = 9 circuit regions, N = 10 circuit regions, etc.

[0083] Fig. 4 shows a schematic block diagram of a radio-frequency circuit 100 with N = 3 circuit regions, according to an embodiment of the present invention. In addition to the N = 3 circuit regions 1021 - 102N (N = 3), the radio-frequency circuit comprises M = 2 waveguides 104i - 104 M (M = 2).

[0084] The first waveguide 104i is designed to guide a first electromagnetic alternating signal 106i coupled in at a first coupling point 116i of the first waveguide 104i to a first coupling-out point P1 at which a first signal 108i, such as an alternating voltage or an alternating current, is coupled out of the first waveguide 104i, wherein the first coupling-out point P1 lies in the second circuit region 1022, wherein the first waveguide 104i is designed to guide the first electromagnetic alternating signal away from the first coupling-out point P1 to a first termination point 110i at which the first waveguide 104i is terminated, wherein the first termination point 110i lies in the first circuit region 102i, so that a power loss resulting from a termination of the first waveguide 104i is introduced into the first circuit region 102i.

[0085] A second coupling point 1162 of the second waveguide 1042 and the first coupling point P1 of the first waveguide 104i are connected to one another via a first coupler 122i located in the second circuit region 1022, wherein the first coupler 122i is designed to couple the first signal 108i coupled out of the first waveguide 104i into the second waveguide 1042 as a second electromagnetic alternating signal 1062.

[0086] The second waveguide 1042 is designed to guide the second electromagnetic alternating signal 1062 to a second coupling-out point P2 at which a second signal 1082, such as an alternating voltage or an alternating current, is coupled out of the second waveguide 1042, wherein the second coupling-out point P2 lies in the third circuit region 1023, wherein the second waveguide 1042 is designed to guide the second electromagnetic alternating signal away from the second coupling-out point P2 to a second termination point HO2, at which the second waveguide 1042 is terminated, wherein the second termination point HO2 lies in the first circuit region 1021, so that a power loss which arises due to a termination of the first waveguide 104i is introduced into the first circuit region 102i.Alternatively, the second termination point 110i may also be located in the second circuit region 1022, so that a power loss resulting from a termination of the second waveguide 1042 is introduced into the second circuit region 1022.

[0087] As shown by way of example in Fig. 4, the first waveguide 104i and the second waveguide 1042 can each be terminated by a terminating resistor 112i and 1122. Alternatively, of course, the respective waveguides can each serve as a termination, as described above with reference to Figs. 2 and 3.

[0088] The first alternating electromagnetic signal 116i may be provided by a signal source that may be part of the radio-frequency circuit 100 or may be external to the radio-frequency circuit 100, as described above with reference to Figs. 2 and 3.

[0089] The signal IO82 coupled out of the second waveguide 1042 can, for example, be used to supply an electrical or electronic component located in the third circuit region 102a. Alternatively or additionally, the signal IO82 coupled out of the second waveguide 1042 can also be coupled into a third waveguide via a second coupler as a third electromagnetic alternating signal, e.g., in embodiments in which the high-frequency circuit 100 has a fourth circuit region and the third electromagnetic alternating signal is to be guided to a third point within the fourth circuit region. In this case, an electrical or electronic component of the fourth circuit region can then be supplied, or alternatively or additionally, coupling into another waveguide can occur again via a corresponding coupler, etc.

[0090] Two possible applications of the high-frequency circuit are described in more detail below. The first application relates to the control of an intensity modulator, where the high-frequency circuit can have two (N = 2) circuit regions. The second application relates to a signal feed for a quantum computer, where the high-frequency circuit can have more than two (N > 2) circuit regions. 1. of an intensity modulator

[0091] The embodiments described herein for dislocated low-reflection termination can be applied, for example, to high-frequency circuits for controlling a quantum computer.

[0092] Laser pulses are required to operate a form of quantum computer. These laser pulses are generated by modulating the intensity of a continuous-wave laser (also known as a cw laser) using intensity modulators.

[0093] For this purpose, the optical laser signal and an electrical modulation signal are fed to the intensity modulator as input signals. To reliably control the intensity of the laser signal at the output and thus the pulse shape, a defined electrical quantity (e.g., voltage, current, power) must be applied to the modulator as a modulation signal. Since the properties of the intensity modulator vary greatly with temperature, it is also necessary to operate the modulator at as constant a temperature as possible.

[0094] In some embodiments, it is therefore advisable to supply the modulation signal in the form of an electromagnetic signal on a waveguide structure, decouple the portion of the signal used to operate the modulator, and guide the signal using the waveguide structure into a region where thermal influences can be tolerated. In this region, the waveguide can be terminated with a low-reflection characteristic impedance. A sketch illustrating the arrangement for four signal feeds is shown in Fig. 5.

[0095] In detail, Fig. 5 shows a schematic block diagram of a radio frequency circuit 100 with integrated intensity modulators 130 for modulating optical laser signals and waveguides 104a - 104d for supplying control signals for controlling the integrated intensity modulators 130, according to an embodiment of the present invention.

[0096] In Fig. 5, four waveguides 104a-104d are shown as examples for supplying four control signals (electromagnetic alternating signals) from four signal sources 118a-118d for controlling the integrated intensity modulators 130. However, it should be noted that the invention is not limited to such embodiments. Rather, in embodiments, the high-frequency circuit 100 can have at least one waveguide (i.e., one waveguide or multiple waveguides, e.g., 2, 3, 5, 10, 15, 20, etc. waveguides) for supplying at least one control signal from at least one signal source.

[0097] Each of the four waveguides 104a-104d is configured, as already described in detail with reference to Figs. 2 and 3, to guide a respective electromagnetic alternating signal from a respective signal source 118a-118d to a respective output point Pa-Pd of the respective waveguide 104a-104d, at which a respective signal is output from the respective waveguide 104a-104d via an output structure 132 and fed to the integrated intensity modulators 130. Furthermore, the respective waveguides 104a-104d are configured to guide the respective electromagnetic alternating signals away from the respective output points Pa-Pb to respective termination points at which the respective waveguides 104a-104d are terminated via respective termination resistors (or load resistors) 118a-118d.The decoupling points Pa - Pd are located in the second circuit region 1022, whereas the termination points and thus also the termination resistors are located in the first circuit region 102i, so that the power losses resulting from the respective terminations are introduced into the first circuit region 102i.

[0098] In other words, Fig. 5 shows an exemplary waveguide structure for driving intensity modulators, illustrated for four signal feeds. The load resistors represent the low-reflection termination with the line characteristic impedance. These are located in a part of the circuit where an increase in temperature does not negatively affect the circuit's properties. If necessary, the load resistors can also be located in a region of the circuit that can be easily cooled.

[0099] 2. Signal supply for a quantum computer

[0100] To reduce the thermal noise of the signal source, thermalized attenuators are conventionally used at different temperature levels of the signal feed for a quantum computer [1], as shown in Fig. 6.

[0101] In detail, Fig. 6 shows a schematic block diagram of a conventional signal feed 20 for a quantum computer for reducing thermal noise with attenuators at different temperature levels. As can be seen in Fig. 6, n temperature levels 24i - 24 are used between signal source 14 and DUT 22 (DUT = Device Under Test). n used, with each temperature level 24i - 24 n an attenuator 26i - 26 n to attenuate the thermal noise from the signal source 14 to the DUT 22.

[0102] Since noise power is proportional to temperature, cooler attenuators introduce less noise into the system. For the noise voltage V RaU sch applies: where T is the temperature in K, f is the center frequency, B is the system bandwidth, R is the system impedance, h is the Planck constant (Planck's constant), and k is the Boltzmann constant.

[0103] A large part of the signal and noise power is reduced by the attenuation at the different temperature levels 24i - 24 n converted into heat. Since the cooling capacity of the system is limited, this concept is only feasible for a small number of lines.

[0104] 2.1 A large part of the power is not lost at the colder temperature levels, but at the warmer temperature levels

[0105] To reduce thermal noise without converting the majority of the signal and noise power into heat at the colder temperature stages of a system, a system with directional couplers can be used in exemplary embodiments. The signal and noise attenuation can be achieved via the coupling attenuation of a directional coupler. The majority of the signal and noise power passes through the coupler's through path and is absorbed at a higher temperature. Only a very small amount of power reaches the coupler's insulated port. Only this power is absorbed at the colder temperature stages to ensure low noise input from the thermal noise of the absorber. This means that only a small portion of the input power is converted into heat in the cooling system, yet the noise power is still significantly reduced.

[0106] In the following, the difference between conventional noise reduction using attenuators at different temperature levels and noise reduction using directional couplers at different temperature levels is explained using exemplary calculations.

[0107] For the example calculation, an attenuator 40 is assumed, as shown in Fig. 7 with an input noise power P290K, an attenuation of -20 dB at 4K and an output noise power of P29OK -20 dB + P4K-

[0108] System impedance 50R, system bandwidth 8GHz

[0109] P290K = -75 dBm

[0110] P4K = -94 dBm

[0111] Ptotai = -91 dBm

[0112] Noise reduction with thermalized directional coupler

[0113] For the example calculation, a directional coupler 50 is assumed, as shown in Fig. 8. In detail, Fig. 8 shows a schematic block diagram of a directional coupler 50 using microstrip technology, with the assignment of the individual ports. The directional coupler 50 comprises an input port 52 as the signal input, a through port 54 that is terminated, a coupled port 56 as the signal output, and an isolated port 58 that is terminated.

[0114] System impedance 50R, system bandwidth 8GHz

[0115] Coupler: coupling factor -20dB, directivity -40dB

[0116] P290K = -75dBm

[0117] Input — P290K -20dB

[0118] PDU passage — P290K - 20dB — 40dB

[0119] Plsolated — P4K

[0120] Ptotai = -91 dBm The total noise power P totai at the lowest temperature level is the same in both cases. However, with the attenuator, a large portion of the signal and noise conduction is converted to heat at the lowest temperature level, while with the directional coupler solution, the power is dissipated at warmer temperature levels.

[0121] In the following, an embodiment of a signal feed for a quantum computer with directional couplers at different temperature levels is explained in more detail with reference to Fig. 9.

[0122] In detail, Fig. 9 shows a schematic block diagram of a high-frequency circuit 100 with several circuit regions with different temperature levels for signal supply for a quantum computer. As can be seen in Fig. 9, the high-frequency circuit 100 comprises N circuit regions 102i - 102N, wherein each circuit region operates at a different temperature level. In detail, the first circuit region 102i operates (e.g., at a zeroth temperature level) at a room temperature TR, wherein the second circuit region 1022 operates at a first temperature level with a first temperature Ti, wherein the first temperature Ti is lower than the room temperature TR, wherein the third circuit region 102a operates at a second temperature level with a second temperature T2, wherein the second temperature T2 is lower than the first temperature Ti, wherein the N minus first circuit region 102N-I operates at an nth temperature level with an nth temperature T nworks, where the n-th temperature T n is less than n minus first temperature T n -i of the N minus second circuit region, wherein the N-th circuit region operates at a DUT temperature TDUT, wherein the DUT temperature is less than or equal to the n-th temperature T n is.

[0123] As can be further seen in Fig. 9 and has also already been described with reference to Fig. 4, the first waveguide 104i can be designed to guide a first electromagnetic alternating signal provided by the signal source 118 to a first coupling-out point P1 at which a first signal IO81, such as an alternating voltage or an alternating current, is coupled out of the first waveguide 104i, wherein the first coupling-out point P1 lies in the second circuit region 1022, wherein the first waveguide 104i is designed to guide the first electromagnetic alternating signal away from the first coupling-out point P1 to a first termination point 110i at which the first waveguide 104i is terminated, wherein the first termination point 110i lies in the first circuit region 102i, so that a power loss which arises due to a termination of the first waveguide 104i is introduced into the first circuit region 102i.A second coupling point of the second waveguide 1042 and the first coupling point P1 of the first waveguide 104i are connected to one another via a first coupler 122i, which is located in the second circuit region 1022, wherein the first coupler 122i is designed to couple the first signal coupled out of the first waveguide 104i into the second waveguide 1042 as a second electromagnetic alternating signal.

[0124] As can be seen in Fig. 9, a first section of the first waveguide 104i can be connected to an input port of the first coupler 122i, and a second section of the first waveguide 104i can be connected to a through port of the first coupler 122i. Furthermore, a first section of the second waveguide 104i can be connected to a coupling port of the first coupler 122i.

[0125] The second waveguide 1042 is designed to guide the second electromagnetic alternating signal IO62 to a second coupling-out point P2 at which a second signal, such as an alternating voltage or an alternating current, is coupled out of the second waveguide 1042, the second coupling-out point P2 being located in the third circuit region 102a, the second waveguide 1042 being designed to guide the second electromagnetic alternating signal away from the second coupling-out point P2 to a second termination point HO2 at which the second waveguide 1042 is terminated, the second termination point HO2 being located in the first circuit region 102i, so that a power loss which arises due to a termination of the first waveguide 104i is introduced into the first circuit region 102i.

[0126] A third coupling point of the third waveguide 1042 and the second coupling point P2 of the second waveguide 1042 are connected to one another via a second coupler 1222 located in the third circuit region 1023, wherein the second coupler 1222 is configured to couple the second signal coupled out of the second waveguide 1042 into the third waveguide 1043 as a third electromagnetic alternating signal.

[0127] As can be seen in Fig. 9, the first section of the second waveguide 1042 can be connected to an input port of the second coupler 1222, wherein a second section of the second waveguide 1042 can be connected to a through port of the second coupler 1222. Furthermore, a first section of the third waveguide 1043 can be connected to a coupling port of the second coupler 1222 and can be configured to guide the third electromagnetic alternating signal to an output point in the third circuit region, where an output signal is in turn coupled into another waveguide via another coupler, etc.

[0128] In other words, Fig. 9 shows a schematic view of a high-frequency circuit for reducing thermal noise with directional couplers at different temperature levels or for noise reduction over several temperature levels with directional couplers and low-reflection terminations.

[0129] In embodiments, thermal noise can be reduced or even minimized towards lower temperatures.

[0130] In exemplary embodiments, the majority of the heat loss occurs at a different location, which alleviates the cooling problem of the colder temperature levels.

[0131] In the examples there is more than one temperature level.

[0132] In exemplary embodiments, signal and thermal noise power is attenuated at decreasing temperatures by the coupling loss of a directional coupler. The majority of the electrical power passes through the coupler's through-path and is converted into heat with low reflection at a warmer temperature level.

[0133] In some examples, the power lines used to drain the power may be of poorer quality, thus resulting in higher losses. This could potentially result in a size advantage.

[0134] In some embodiments, a lossy cable can have sufficient attenuation at higher temperatures, so that a separate sump is not necessary. It is conceivable to use a cable with a conductor made of a superconducting material that is no longer superconducting at higher temperatures and thus has high losses.

[0135] In existing designs, the limited cooling capacity of individual temperature levels has resulted in the power loss being distributed across multiple temperature levels. The directional coupler concept allows the majority of the power loss to be absorbed at the warmest temperature level, which typically has the greatest cooling capacity. This allows the number of attenuators with different temperatures to be reduced.

[0136] In embodiments, directional couplers and the RF terminations of the isolated ports can also be integrated into the cable, as shown in Fig. 10. In detail, Fig. 10 shows a schematic block diagram of a cable 150, wherein at least the i-th output coupling point of the i-th waveguide, a directional coupler as the i-th coupler 122, and the (i+1)-th input coupling point of the (i+1)-th waveguide are integrated into the cable 150. In other words, Fig. 10 shows a cable with multiple waveguides, an integrated directional coupler, and an integrated RF termination.

[0137] In embodiments, the directional coupler can also be replaced by a power splitter and a directive element, as shown in Fig. 11. In detail, Fig. 10 shows a schematic block diagram of a cable 150, wherein at least the i-th output coupling point of the i-th waveguide, a directive element and a power splitter as the i-th coupler 122, and the (i+1)-th input coupling point of the (i+1)-th waveguide are integrated into the cable 150. In other words, Fig. 11 shows a cable with multiple waveguides, an integrated power splitter, and an integrated directive element.

[0138] Although some aspects have been described in the context of a device, it should be understood that these aspects also represent a description of the corresponding method, so that a block or component of a device can also be understood as a corresponding method step or as a feature of a method step. Analogously, aspects described in the context of or as a method step also represent a description of a corresponding block, detail, or feature of a corresponding device. Some or all of the method steps may be performed by (or using) a hardware apparatus, such as a microprocessor, a programmable computer, or an electronic circuit. In some embodiments, some or more of the key method steps may be performed by such an apparatus.

[0139] Depending on specific implementation requirements, embodiments of the invention may be implemented in hardware or software. The implementation may be performed using a digital storage medium, such as a floppy disk, a DVD, a Blu-ray Disc, a CD, a ROM, a PROM, an EPROM, an EEPROM, or a FLASH memory, a hard disk, or other magnetic or optical storage device storing electronically readable control signals that can interact or cooperate with a programmable computer system to perform the respective method. Therefore, the digital storage medium may be computer-readable.Some embodiments according to the invention thus comprise a data carrier having electronically readable control signals capable of interacting with a programmable computer system such that one of the methods described herein is carried out.

[0140] In general, embodiments of the present invention may be implemented as a computer program product having a program code, wherein the program code is effective to perform one of the methods when the computer program product is run on a computer.

[0141] The program code can, for example, also be stored on a machine-readable medium.

[0142] Other embodiments include the computer program for performing one of the methods described herein, wherein the computer program is stored on a machine-readable carrier.

[0143] In other words, an embodiment of the method according to the invention is thus a computer program which has a program code for carrying out one of the methods described herein when the computer program runs on a computer.

[0144] A further embodiment of the method according to the invention is thus a data carrier (or a digital storage medium or a computer-readable medium) on which the computer program for performing one of the methods described herein is recorded. The data carrier, the digital storage medium, or the computer-readable medium is typically physical and / or non-perishable or non-transient.

[0145] A further embodiment of the method according to the invention is thus a data stream or a sequence of signals that represents the computer program for carrying out one of the methods described herein. The data stream or the sequence of signals can be configured, for example, to be transferred via a data communication connection, for example via the Internet. A further embodiment comprises a processing device, for example a computer or a programmable logic component, that is configured or adapted to carry out one of the methods described herein.

[0146] A further embodiment comprises a computer on which the computer program for performing one of the methods described herein is installed.

[0147] A further embodiment according to the invention comprises a device or system designed to transmit a computer program for performing at least one of the methods described herein to a recipient. The transmission can be electronic or optical, for example. The recipient can be, for example, a computer, a mobile device, a storage device, or a similar device. The device or system can, for example, comprise a file server for transmitting the computer program to the recipient.

[0148] In some embodiments, a programmable logic device (e.g., a field-programmable gate array, an FPGA) may be used to perform some or all of the functionalities of the methods described herein. In some embodiments, a field-programmable gate array may cooperate with a microprocessor to perform any of the methods described herein. In general, in some embodiments, the methods are performed by any hardware device. This may be general-purpose hardware such as a computer processor (CPU) or method-specific hardware such as an ASIC.

[0149] The devices described herein may be implemented, for example, using a hardware apparatus, or using a computer, or using a combination of a hardware apparatus and a computer.

[0150] The devices described herein, or any components of the devices described herein, may be implemented at least partially in hardware and / or in software (computer program).

[0151] The methods described herein may be implemented, for example, using a hardware apparatus, or using a computer, or using a combination of a hardware apparatus and a computer. The methods described herein, or any components of the methods described herein, may be carried out at least partially by hardware and / or by software. The above-described embodiments are merely illustrative of the principles of the present invention. It is understood that modifications and variations of the arrangements and details described herein will be apparent to others skilled in the art. Therefore, it is intended that the invention be limited only by the scope of the following claims and not by the specific details presented in the description and explanation of the embodiments herein.

[0152] Literaturverzeichnis

[0153] EPJ Quantum Technology 6(1) - „Engineering cryogenic setups for 100-qubit scale superconducting circuit systems“

Claims

Patent claims 1. High-frequency circuit [e.g. high-frequency waveguide structure], with the following features: a first circuit region, a second circuit region, and a waveguide, wherein the waveguide is designed to guide an electromagnetic alternating signal to a coupling-out point at which a signal [e.g. alternating voltage, alternating current] is coupled out of the waveguide, wherein the coupling-out point lies in the second circuit region, wherein the waveguide is designed to guide the electromagnetic alternating signal away from the coupling-out point to a termination point at which the waveguide is terminated, wherein the termination point lies in the first circuit region, so that a power loss which arises at the termination point [e.g. by a termination of the waveguide] is introduced [e.g. at least 80% or 90%] into the first circuit region.

2. High-frequency circuit according to the preceding claim, wherein heat generated by the power loss acts largely [eg at least 80% or 90%] on the first circuit region.

3. High-frequency circuit according to one of the preceding claims, wherein the first circuit region is designed to be able to operating temperature, wherein the second circuit region is configured to operate at a second working temperature, where the second working temperature is lower than the first working temperature.

4. A high-frequency circuit according to any one of the preceding claims, wherein the first circuit region is configured to operate within a first permissible operating temperature range, wherein the second circuit region is configured to operate within a second permissible operating temperature range, wherein the second permissible operating temperature range is smaller than the first permissible operating temperature range.

5. High-frequency circuit according to claim 4, wherein significantly smaller [eg at least by a factor of 2, 3, 4, 5 or 10] temperature differences [eg around a first target temperature] are permissible within the second temperature range than within the first temperature range.

6. The high-frequency circuit according to claim 4 or 5, wherein a second operating temperature of the second operating temperature range is lower than a first operating temperature of the first operating temperature range.

7. A high-frequency circuit according to any one of the preceding claims, wherein the first circuit region and the second circuit region are thermally insulated from each other.

8. High-frequency circuit according to one of the preceding claims, wherein a length of the waveguide between the coupling-out point and the termination point is at least one-tenth of a wavelength of the electromagnetic alternating signal.

9. High-frequency circuit according to one of the preceding claims, wherein at least one electronic component arranged in the second circuit region is supplied via the signal coupled out of the waveguide at the coupling-out point.

10. High-frequency circuit according to one of the preceding claims, wherein the signal is coupled out at the coupling point via a coupling out device.

11. High-frequency circuit according to the preceding claim, wherein the decoupling device is designed to couple the signal by means of a voltage tap, a power decoupling, a tap, a voltage divider or a coupler.

12. High-frequency circuit according to one of the preceding claims, wherein the waveguide is terminated at the termination point by a load resistance [e.g. line wave resistance], or wherein the waveguide serves as a terminating resistance.

13. High-frequency circuit according to one of the preceding claims, wherein the waveguide has a coupling point at which the electromagnetic alternating signal is coupled into the waveguide.

14. High-frequency circuit according to the preceding claim, wherein the high-frequency circuit has a signal source configured to generate the alternating electromagnetic signal.

15. High-frequency circuit according to one of the preceding claims, wherein the high-frequency circuit comprises an intensity modulator, wherein the intensity modulator is arranged in the second circuit region, wherein the intensity modulator is supplied via the signal coupled out of the waveguide at the coupling point.

16. A high-frequency circuit according to any one of the preceding claims, wherein the waveguide comprises a microstrip line or a coaxial cable.

17. High-frequency circuit, having the following features: N circuit regions, where N is a natural number greater than or equal to two, N > 2, and M waveguides, where M is a natural number equal to N minus one, M = N-1 , where for a natural number i from one to N minus one, i = {1 , ..., N-1} an i-th waveguide of the M waveguides is designed to guide an i-th electromagnetic alternating signal to an i-th output point at which an i-th signal [e.g. alternating voltage, alternating current] is coupled out of the i-th waveguide, where the i-th output point lies in the (i+1)-th circuit region, and the i-th waveguide is designed to guide the i-th electromagnetic alternating signal away from the i-th output point to an i-th termination point at which the i-th waveguide is terminated, where the i-th termination point lies in one of an (i=1)-th to i-th circuit region of the N circuit regions, so that a power loss that occurs at the i-th termination point [e.g. by an i-th termination of the i-th waveguide] is created, [e.g.at least 80% or 90%] into the circuit region in which the i-th termination point is located.

18. A high-frequency circuit according to claim 17, wherein for a natural number k from two to N, k = {2, ..., N}, a k-th circuit region of the N circuit regions is configured to operate at a k-th operating temperature, the k-th operating temperature being lower than a (k-1)-th operating temperature at which a (k-1)-th circuit region of the N circuit regions operates.

19. High-frequency circuit according to one of claims 17 to 18, where N is a natural number greater than or equal to three, N > 3, where for a natural number i from one to N minus one, an (i+1)th coupling point of the (i+1)th waveguide and the i-th coupling point of the i-th waveguide are connected to one another via an i-th coupler located in the (i+1)th circuit region, the i-th coupler being designed to couple the i-th signal coupled out from the i-th waveguide into the (i+1)th waveguide as an (i+1)th electromagnetic alternating signal.

20. A high-frequency circuit according to any one of claims 17 to 19, wherein for a natural number k from two to N, a thermal noise of the k-th circuit region of the N circuit regions is lower than a thermal noise of the (k-1)-th circuit region.

21. A high-frequency circuit according to any one of claims 17 to 20, wherein for a natural number k from two to N minus one, a signal power and / or noise power from the (k-1)th circuit region to the (k+1)th circuit region is attenuated by the coupling attenuation of the i-th coupler in the k-th circuit region.

22. High-frequency circuit according to one of claims 17 to 21, wherein at least one waveguide of the M waveguides has a first waveguide section which runs between the coupling-in point of the respective waveguide and the coupling-out point of the respective waveguide, wherein the at least one waveguide has a second waveguide section which runs between the coupling-out point of the respective waveguide and the termination point of the respective waveguide, wherein the second waveguide section has a higher attenuation or higher losses [e.g. poorer quality] than the first waveguide section.

23. High-frequency circuit according to claim 22, wherein the second waveguide section may comprise superconducting material.

24. High-frequency circuit according to one of claims 17 to 23, wherein the high-frequency circuit has at least one cable, the following features being integrated into the cable: the i-th coupling point of the i-th waveguide, the i-th coupler, the (i+ 1)-th coupling point of the (i+ 1)-th waveguide.

25. A high-frequency circuit according to any one of claims 17 to 24, wherein the i-th coupler is implemented by means of a directional coupler, or wherein the i-th coupler is implemented by means of a power splitter and a directive element.

26. A high-frequency circuit according to any one of claims 17 to 25, wherein the high-frequency circuit is a signal feed for a quantum computer.

27. Quantum computer, comprising: a laser signal source configured to generate a laser signal; a modulation signal source configured to generate an electromagnetic alternating signal; an intensity modulator configured to modulate an intensity of the laser signal on the basis of the electromagnetic alternating signal; and a radio-frequency circuit according to one of claims 1 to 15, wherein the intensity modulator is arranged in the second circuit region of the radio-frequency circuit, or according to one of claims 17 to 26, wherein the Intensity modulator is arranged in the Nth circuit region of the high-frequency circuit.

28. The quantum computer of claim 27, wherein the second or Nth circuit region is configured to operate at an operating temperature of 1 K or less.

29. Quantum computer according to one of claims 27 to 28, wherein the laser signal source is configured to generate a pulsed laser signal or continuous wave laser signal as the laser signal.

30. A quantum computer according to any one of claims 27 to 29, wherein the quantum computer comprises: a plurality of radio frequency circuits according to any one of claims 1 to 15 or any one of claims 17 to 26 for a plurality of qubits.

31. A quantum computer according to any one of claims 27 to 30, wherein the quantum computer comprises a radio frequency circuit according to any one of claims 17 to 26, where N is a natural number greater than or equal to three, N > 3, where for a natural number k from two to N, k = {2, ... , N}, a k-th circuit region of the N circuit regions is configured to operate at a k-th operating temperature, the k-th operating temperature being less than a (k-1)-th operating temperature at which a (k-1)-th circuit region of the N circuit regions operates.

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