Apparatus, Structures, and Methods for Electromagnetic Isolation of Quantum Computing Circuits

Abstract

Apparatus and methods are disclosed for facilitating first and second frequency filtering along with non-reciprocal frequency transformation for electromagnetic isolation.

Description

[Technical Field]

[0001] The present invention relates to electromagnetic isolation for quantum computing. [Background technology]

[0002] The readout chain of a quantum computer typically requires a large number of large and expensive circulators to isolate the quantum processing unit from backaction noise from the following semiconductor amplifiers in the high-temperature stage of the cryostat, and these circulators also have a large thermal mass and require a large mechanical space.

[0003] Several alternative implementations of circulators exist. Typically, these rely on the Hall effect and related phenomena. These technologies are not yet mature and often face significant challenges in terms of reliability, impedance matching, dynamic range, bandwidth, and sensitivity to external factors. Summary of the Invention [Problem to be solved by the invention]

[0004] The aim is to mitigate the above drawbacks.

[0005] The goal is also to eliminate the need for such a circulator altogether. [Means for solving the problem]

[0006] According to the present disclosure, irreversible When frequency translation is combined with frequency filtering before and after the frequency translation, irreversible It has been shown that frequency conversion can be effectively used to isolate quantum computing circuits.

[0007] According to a first aspect, an apparatus for electromagnetic isolation of, for example, quantum computing circuits is provided. The apparatus includes a first frequency filter that can be configured to transmit signals having frequencies within a first low frequency range and to terminate signals having frequencies within a first high frequency range. The apparatus also includes a second frequency filter that can be configured to block signals having frequencies within a second low frequency range and to transmit signals having frequencies within a second high frequency range. The apparatus includes a frequency converter having a first input / output that can be coupled to the first frequency filter and a second input / output that can be coupled to the second frequency filter. The frequency converter is configured to relatively suppress or relatively enhance an output signal of the frequency converter at the first input / output of the frequency converter having a frequency within the first low frequency range with respect to an output signal of the frequency converter at the second input / output of the frequency converter having a frequency within the second high frequency range, for example, in response to an external drive signal to or for the frequency converter, with respect to signal transmission between the first input / output and the second input / output. irreversible The device may be configured to be non-reciprocal. This allows a read signal having a read frequency to be transmitted through the device so that, at the input, the read frequency corresponds to the input frequency, and, at the output, the read frequency corresponds to an output frequency different from the input frequency. A frequency range outside the input frequency may be blocked by a first frequency filter if the first input / output terminal is an input terminal for the read signal, or by a second frequency filter if the second input / output terminal is an input terminal for the read signal. Correspondingly, a frequency range outside the output frequency may be blocked by a first frequency filter if the first input / output terminal is an output terminal for the read signal, or by a second frequency filter if the second input / output terminal is an output terminal for the read signal. Importantly, any backaction signal can be reduced even when it has a frequency corresponding to the output frequency of the read signal. This allows irreversible The frequency conversion facilitates attenuation of the backaction signal at least relative to the readout signal.

[0008] The frequency conversion is irreversible It has been found that this can be effectively accomplished by an amplifier operable in a magnetic field, thereby amplifying signal transmission in a forward direction, such as the read direction, and attenuating signal transmission in a back action direction. In addition, no magnetic components are required for electromagnetic isolation.

[0009] In one embodiment, in response to an external signal, the frequency converter is configured to generate gain for its output signal having a frequency within a second high frequency range at the second input / output end of the frequency converter and / or generate attenuation for its output signal having a frequency within a first low frequency range at the first input / output end of the frequency converter. This allows the device to facilitate transmission of a read signal in a direction where the first input / output end is the read signal input and the second input / output end is the read signal output, while suppressing transmission of any backaction signal in the opposite direction. In this way, the frequency of the read signal can be upconverted by the device while suppressing backaction.

[0010] In one embodiment, in response to an external signal, the frequency converter is configured to generate gain for its output signal having a frequency within a first low frequency range at a first input / output end of the frequency converter and / or generate attenuation for its output signal having a frequency within a second high frequency range at a second input / output end of the frequency converter. This allows the device to facilitate transmission of a read signal in a direction in which the second input / output end is the read signal input and the first input / output end is the read signal output, while suppressing transmission of any backaction signal in the opposite direction. In this way, the frequency of the read signal can be downconverted by the device while suppressing backaction.

[0011] Therefore, as shown, the frequency converter can be an amplifier, for example, as in the previous two embodiments, which has an additional advantage for quantum circuits, as it makes it easier for noise in the amplification to reach the quantum limit.

[0012] In one embodiment, the frequency converter comprises or consists of one or more traveling-wave parametric amplifiers (TWPAs). It has been found that TWPAs can be configured to perform or facilitate any or all of the actions associated with frequency conversion. This includes providing gain to the readout signal while attenuating backaction signals, which may have the same or corresponding frequency as the readout signal. TWPAs have also been found to be particularly effective for use in quantum computing circuits. For example, they may provide extended bandwidth and / or dynamic range. Additionally, TWPAs are a relatively mature technology and therefore can be easily and reliably applied in such situations. Compared to other technologies, TWPAs may easily achieve good noise temperature and isolation.

[0013] In one embodiment, the frequency converter comprises or consists of one or more tunable phase shifters and / or Josephson parametric converters. It is understood that such devices can be configured to perform or facilitate any or all of the actions associated with frequency conversion. Josephson parametric converters can provide amplification and / or non-amplification between multiple different frequency modes.

[0014] In one embodiment, the first frequency filter and / or the second frequency filter are passive filters. This has been found to facilitate simple and reliable frequency filtering that can still be used in the context of quantum computing circuits. In particular, isolation can be achieved without unnecessary power consumption.

[0015] In one embodiment, the first low frequency range corresponds to the second low frequency range and / or the first high frequency range corresponds to the second high frequency range, and accordingly the first frequency filter and the second frequency filter may be frequency mirrored relative to each other.

[0016] According to a second aspect, a structure is disclosed that can be used for electromagnetic isolation, for example, for quantum computing circuits. The structure includes a device according to the first aspect or any of its embodiments, alone or in any combination. The structure also includes a third frequency filter configured to transmit signals having frequencies within a third frequency range and to block signals having frequencies within a frequency range outside the third frequency range. The third frequency range can partially or completely coincide with either the first frequency range or the second frequency range, whichever is further from the third frequency filter in a signal transmission direction across the structure. This allows the third frequency filter and the first or second frequency filter to form signal entry and exit points through which signals of the same or corresponding frequencies can be transmitted and other signals can be blocked. The structure also includes a second frequency converter coupled between the device and the third frequency filter. This is done so that in response to an input signal having an input frequency provided to the device, the structure is configured to generate an output signal from the third frequency filter having an output frequency substantially corresponding to the input frequency, or in response to an input signal having an input frequency provided to the third frequency filter, the structure is configured to generate an output signal from the device having an output frequency substantially corresponding to the input frequency. In a first alternative, the third frequency filter is configured to provide a signal entry point for the structure, and in a second alternative, it is configured to provide a signal exit point for the structure. Both alternatives allow the structure to provide electromagnetic isolation without changing or substantially changing the frequency of a signal, such as a read signal, when transmitted through the structure. Also, the second frequency converter may be configured to change the frequency of a signal, e.g., in response to an external drive signal, with respect to the signal transmission direction. irreversibleThis construction may also significantly improve insulation.

[0017] According to a third aspect, an arrangement is disclosed that can also be used for electromagnetic isolation of, for example, quantum computing circuits, comprising a quantum processing unit coupled, alone or in any combination, to one or more devices according to the first aspect or any of its embodiments, and / or an arrangement according to the second and / or third aspect for preventing backaction noise to the quantum processing unit.

[0018] According to a fourth aspect, a method for electromagnetic isolation of, for example, quantum computing circuits is disclosed. The method includes performing or facilitating frequency filtering in a first frequency filter, e.g., transmitting signals having frequencies in a first low frequency range and blocking signals having frequencies in a first high frequency range. The method also includes performing or facilitating frequency filtering in a second frequency filter, e.g., blocking signals having frequencies in a second low frequency range and transmitting signals having frequencies in a second high frequency range. The method includes performing or facilitating frequency translation, e.g., in a frequency converter as disclosed herein, between a first input / output coupled to the first frequency filter and a second input / output coupled to the second frequency filter. The frequency conversion may be performed in response to an external driving signal for the frequency conversion, for example, in relation to signal transmission between the first input / output terminal and the second input / output terminal, to relatively suppress or relatively enhance an output signal of the frequency conversion having a frequency within the first low frequency range at the first input / output terminal with respect to an output signal of the frequency conversion having a frequency within the second high frequency range at the second input / output terminal. irreversibleIn this method, a read signal may be received as an input signal to a first frequency filter and provided as an output signal from the second frequency filter, such that the first input / output terminal serves as an input terminal for the read signal and the second input / output terminal serves as an output terminal for the read signal. Alternatively, a read signal may be received as an input signal to a second frequency filter and provided as an output signal from the first frequency filter, such that the second input / output terminal serves as an input terminal for the read signal and the first input / output terminal serves as an output terminal for the read signal.

[0019] In one embodiment, in response to an external signal, the frequency conversion generates gain for its output signal at the second input / output end having a frequency within a second high frequency range and / or generates attenuation for its output signal at the first input / output end having a frequency within a first low frequency range.

[0020] In one embodiment, in response to an external signal, the frequency conversion generates gain for its output signal having a frequency within a first low frequency range at the first input / output end and / or generates attenuation for its output signal having a frequency within a second high frequency range at the second input / output end.

[0021] In one embodiment, the frequency conversion is performed or facilitated by one or more traveling wave parametric amplifiers.

[0022] In one embodiment, the frequency conversion is performed or facilitated by one or more tunable phase shifters and / or Josephson parametric converters.

[0023] In one embodiment, the frequency filtering in the first frequency filter and / or the second frequency filter is performed passively.

[0024] In one embodiment, the first low frequency range corresponds to the second low frequency range and / or the first high frequency range corresponds to the second high frequency range.

[0025] According to a fifth aspect, a method is disclosed that can also be used for electromagnetic isolation of, for example, quantum computing circuits. The method includes performing, alone or in any combination, a first method according to the fourth aspect or any of its embodiments. The method also includes facilitating frequency filtering in a third frequency filter, wherein signals having frequencies within a third frequency range are transmitted and signals having frequencies within a frequency range outside the third frequency range are blocked. The method includes, for example, facilitating, in response to an external drive signal, frequency filtering in the third frequency filter and frequency filtering in the first frequency filter or the second frequency filter in relation to a signal transmission direction. irreversible The method further includes facilitating a second frequency translation, which may be performed such that, in response to performing the first method on an input signal having an input frequency, an output signal is generated from the third frequency filter having an output frequency that substantially corresponds to the input frequency, or such that, in response to providing an input signal having the input frequency to the third frequency filter, an output signal is generated from the first frequency filter or the second frequency filter having an output frequency that substantially corresponds to the input frequency.

[0026] This can be achieved by alternating two frequency translations with three frequency filterings, and is applicable to both the configuration of the second aspect and the method of the fifth aspect and their embodiments. The frequency filtering between the other two frequency filterings and the two frequency translations is performed by a frequency filter, i.e., the first filter or the second filter, which may be complementary to the third frequency filter, so that signals having frequencies within the third frequency range can be blocked there. However, these can still be transmitted by the other filter, i.e., the first filter or the second filter, thereby providing a signal entry or exit point for the configuration. Overall, signals having frequencies within the third frequency range can be transmitted before and after the two frequency translations. At the same time, such signals can be blocked between the two frequency translations. Conversely, signals having frequencies within a range outside the third frequency range can be blocked before and after the two frequency translations. At the same time, such signals can be transmitted between the two frequency translations. This signal termination and irreversible Frequency conversion allows for electromagnetic isolation while preserving the signal frequency, especially in the forward direction.

[0027] According to a sixth aspect, a method is disclosed that can also be used for electromagnetic isolation of, for example, quantum computing circuits, comprising performing a method according to the fourth aspect or any of its embodiments, alone or in any combination, and / or performing a method according to the fifth aspect and / or the sixth aspect, to prevent backaction noise to a quantum processing unit.

[0028] It should be understood that the above-described aspects and embodiments can be used in any combination with each other. Some aspects and embodiments can also be combined together to form further embodiments. Features and advantages disclosed in relation to the first, second, and third aspects and their embodiments can also be correspondingly applied to the fourth, fifth, and sixth aspects and their embodiments, respectively.

[0029] The accompanying drawings are included to provide a further understanding of the invention, and constitute a part of this specification, illustrate examples and, together with the description, serve to explain the principles of the disclosure. [Brief explanation of the drawings]

[0030] [Figure 1] 1 illustrates an apparatus and arrangement according to an example. [Figure 2a] FIG. 10 illustrates an example construct. [Figure 2b] FIG. 10 illustrates an example construct. [Figure 3] FIG. 1 illustrates a method according to an example. [Figure 4a] FIG. 1 illustrates a simulation according to an example. [Figure 4b] FIG. 1 illustrates a simulation according to an example. DETAILED DESCRIPTION OF THE INVENTION

[0031] In the accompanying drawings, like reference numerals are used to indicate equivalent or at least functionally equivalent parts.

[0032] The detailed description provided below in connection with the accompanying drawings is intended as an illustration of examples and is not intended to represent the only form in which the examples may be constructed or utilized, however, the same or equivalent functions and structures may be accomplished by different examples.

[0033] 1 illustrates an example of an apparatus 100 according to an embodiment. The apparatus may be used, for example, for electromagnetic isolation of quantum computing circuits. The apparatus includes two or more frequency filters 110, 120, which may be complementary to each other. In particular, two separate signal channels may be provided: a low-frequency signal channel and a high-frequency signal channel. The two frequency filters may ensure that the channels do not overlap in frequency.

[0034] The device includes one or more first frequency filters 110 that can be configured to transmit signals having frequencies within a first low frequency range and to terminate signals having frequencies within a first high frequency range. The first high frequency range and the first low frequency range can be non-overlapping. The first low frequency range and the first high frequency range can be complementary such that all signals having frequencies outside the first low frequency range are blocked and all signals having frequencies within the first low frequency range are transmitted.

[0035] The device also includes one or more second frequency filters 120 that can be configured to block signals having frequencies within a second low frequency range and transmit signals having frequencies within a second high frequency range. The second high frequency range and the second low frequency range can be non-overlapping. The second low frequency range and the second high frequency range can be complementary so that all signals having frequencies outside the second high frequency range are blocked and all signals having frequencies within the second high frequency range are transmitted. The second high frequency range can partially or completely coincide with the first high frequency range. The second low frequency range can partially or completely coincide with the first low frequency range.

[0036] The apparatus 100 comprises a (first) frequency converter 130 (also referred to herein as a “frequency converter”) having a first input / output terminal 132 and a second input / output terminal 134. The frequency converter is bidirectional, converting an input signal received at the first input / output terminal to one or more output signals provided at the second input / output terminal, and converting an input signal received at the second input / output terminal to one or more output signals provided at the first input / output terminal. The input signal has an input frequency. The one or more output signals may have one or more output frequencies. Importantly, the frequency converter is configured to provide an output signal at the second input / output terminal having a frequency within a second, high frequency range in response to receiving an input signal at the first input / output terminal having a frequency within a first, low frequency range. Being bidirectional, the frequency converter may also be configured to provide an output signal at the first input / output terminal having a frequency within a first, low frequency range in response to receiving an input signal at the second input / output terminal having a frequency within a second, high frequency range. The frequency converter is capable of preserving the quantum coherence of the signal while performing the conversion.

[0037] The first input / output 132 may be configured to be coupled to the first frequency filter 110. The coupling may be indirect or direct. Similarly, the second input / output 134 may be configured to be coupled to the second frequency filter 120. The coupling may be indirect or direct.

[0038] Thus, the combination is such that a signal 20 having a frequency within a first low frequency range is received as an input signal at a first frequency filter and transmitted through the device 100, and a signal 20 having a frequency within a second high frequency range (f 1,out ) where any or all sub-signals of the input signal having frequencies outside the first low frequency range may be blocked. Also, any sub-signals of the input signal having frequencies outside the second high frequency range (f 2,out ) may be blocked.

[0039] Similarly, the combination is received as an input signal at a second frequency filter 120, which filters out frequencies within a second high frequency range (f 1,in ) is transmitted through the apparatus 100 and is configured to generate from the first frequency filter 110 an output signal having a frequency within a first low frequency range, where the output signal has a frequency (f 2,in ) may be blocked.

[0040] An input signal of device 100, such as a read signal, may be provided to first frequency filter 110 or second frequency filter 120 depending on the orientation of the device. Correspondingly, an output signal of the device, such as a read signal, may be provided from second frequency filter 110 or first frequency filter 120 depending on the orientation of the device. The directionality of frequency converter 130 may indicate the directionality of the device, such that the input signal of device 100 is provided as an input signal to the frequency converter, and the output signal from the frequency converter is provided as an output signal of the device.

[0041] 1, the horizontal axis can be thought of as simply showing the behavior of a signal transmitted through device 100 for different frequencies, with smaller frequencies on the left and larger frequencies on the right. 1,in and f 1,out is f 2,in and f 2,out However, f 1,in and f 1,out may be the same or substantially the same relative to each other. 2,in and f 2,out The same is true for .

[0042] The frequency converter 130 is configured to convert a signal between a first input / output 132 and a second input / output 134 into a irreversibleAs a result, a change in signal amplitude of an input signal provided to the frequency converter may depend on the direction of signal transmission through the frequency converter, i.e., whether the input signal is provided to the first input / output or the second input / output. irreversible The characteristic corresponds to a relative suppression or a relative strengthening of an output signal of the frequency converter having a frequency in a first low frequency range at a first input / output end of the frequency converter with respect to an output signal of the frequency converter having a frequency in a second high frequency range at a second input / output end of the frequency converter, thereby resulting in a symmetry breaking of the signal transmission across the frequency converter and across the entire device 100 depending on the direction of signal transmission across the frequency converter. irreversible The performance may be responsive to an external drive signal to or for the frequency converter. The device may be configured to automatically provide the external drive signal.

[0043] The device 100 may be indirectly or directly coupled to a signal source 10, such as a quantum computing circuit that may include a quantum processing unit. Symmetry breaking allows the device to transmit a first signal, such as a readout signal, in one direction while mitigating or preventing backaction from that signal in the other direction. The first signal may be transmitted from a signal source. Accordingly, the first signal may be a readout signal, such as a readout signal of a quantum computing circuit. The first signal may have a frequency of, for example, 1-20 GHz or 2-10 GHz. The device may be configured for a first signal having a fixed bandwidth, for example, 2-4 GHz or less. The frequency range of the frequency filter may be configured accordingly. The device 100 may be configured to mitigate or prevent backaction from the signal source. The output of the device may be coupled to one or more semiconductor amplifiers, which may be hotter than the input of the device. The device may be configured to mitigate or prevent backaction noise transmitted to a signal source, such as a quantum processing unit.

[0044] As shown in FIG. 1, a second frequency filter 120 filters out frequencies outside the second high frequency range (f 2,in ) can be mitigated or completely prevented from backaction from any or all signals having frequencies (f 1,in ) may also be mitigated or completely prevented. Additionally, the first frequency filter 110 may suppress or block any sub-signals of the signal having frequencies within the first high frequency range that may be transmitted through the frequency converter.

[0045] In FIG. 1 , solid lines indicate a first signal transmitted through the device 100. Dashed lines indicate signals or sub-signals that are suppressed or blocked. For example, the first frequency filter 110 and the second frequency filter 120 can block all signals, including sub-signals, that are not within a frequency range configured to allow transmission of the signal. The frequency converter 130 can be configured to suppress backaction at any or all frequencies. In particular, it can be configured to suppress backaction in a frequency range corresponding to transmission of the first signal through the frequency converter.

[0046] The preferred direction for signal transmission through the device 100, i.e., the forward direction, can be freely selected, and the device can be configured accordingly. The opposite direction, i.e., the reverse direction, can then correspond to backaction. According to a first alternative, the device is configured so that a first signal is transmitted from the first input / output terminal 132 to the second input / output terminal 134, suppressing or blocking backaction in the opposite direction. In this alternative, the frequency converter is configured to generate gain for its output signal having a frequency within a second high frequency range at the second input / output terminal of the frequency converter and / or generate attenuation for its output signal having a frequency within a first low frequency range at the first input / output terminal of the frequency converter in response to an external signal. In this alternative, the signal source 10 can be indirectly or directly coupled to the device at the first frequency filter 110. The signal source is then coupled to the frequency converter 130 via the first frequency filter. The forward direction is from the first frequency filter to the second frequency filter. Thus, the first signal transmitted through the device may correspond to signal 20 in Figure 1, for example as a read signal, the signal source being coupled to the first frequency filter, while signal 30 then corresponds to the backaction signal.

[0047] According to a second alternative, as an alternative or addition to the first alternative, the device is configured such that a first signal is transmitted from the second input / output terminal 134 to the first input / output terminal 132, and back action in the opposite direction is suppressed or blocked. In this alternative, the frequency converter is configured to generate gain for its output signal having a frequency within a first low frequency range at the first input / output terminal of the frequency converter and / or generate attenuation for its output signal having a frequency within a second high frequency range at the second input / output terminal of the frequency converter in response to an external signal. In this alternative, the signal source 10 can be indirectly or directly coupled to the device at the second frequency filter 110. The signal source is then coupled to the frequency converter 130 via the second frequency filter. The forward direction is from the second frequency filter to the first frequency filter. Thus, the first signal transmitted through the device corresponds to signal 30 of FIG. 1, e.g., as a read signal, and the signal source can be coupled to the second frequency filter. On the other hand, signal 20 would then correspond to a backaction signal.

[0048] The external drive signal can determine the threshold frequency 40 at which the input signal of the frequency converter is converted. The threshold frequency can be higher than the first low frequency range and lower than the second high frequency range. Alternatively, the threshold frequency can be higher than the second low frequency range and lower than the first high frequency range. The external drive signal can be provided by pumping, such as optical pumping with three-way or four-way pumping. The pumping frequency of the external drive signal can correspond to the threshold frequency or a multiple thereof. In the case of four-way pumping, the pumping frequency can correspond to the threshold frequency. In the case of three-way pumping, the pumping frequency can correspond to twice the threshold frequency.

[0049] In particularly important embodiments, the frequency converter comprises or consists of one or more traveling-wave parametric amplifiers (TWPAs). As is known, the output signal of a TWPA may include an idler signal having a different frequency from the input signal of the TWPA from which the output signal is generated. In addition to the idler signal, the output signal of the TWPA may also include a signal having the same or substantially the same frequency as the input signal of the TWPA from which the output signal is generated. In view of the present disclosure, the device 100 may be configured to utilize the idler signal to provide the output signal of the device, for example, as a read signal. The idler signal may thereby provide a signal having a frequency within the second high frequency range, according to the first alternative above, or a signal having a frequency within the first low frequency range, according to the second alternative above. This signal may be the output signal of the device. The threshold frequency may correspond to the pump frequency for the TWPA or a multiple thereof. Alternatively or additionally, the frequency converter comprises or consists of one or more tunable phase shifters and / or Josephson parametric converters. For example, the frequency converter may comprise two or more tunable phase shifters in series, which may comprise two or more SQUID loops in series, which may have substantially perfect transmission in series. Two of the phase shifters may be configured to generate, for example, equal and opposite phase shifts. The device may nonlinearly modulate the phase as a function of time, thereby modulating the signal transmission. irreversible The sensor may be configured to be selective, i.e., directionally dependent.

[0050] 2a and 2b show an example of an arrangement 200. The arrangement comprises the device 100. However, the arrangement is configured to maintain, or at least substantially maintain, the signal frequency throughout the arrangement, particularly in the forward direction.

[0051] To this end, the configuration 200 includes at least one additional frequency filter, third frequency filter 210, 220, configured to transmit signals having frequencies within a third frequency range and block signals having frequencies within a frequency range outside the third frequency range. The third frequency range and the frequency range outside the third frequency range may not overlap. The third frequency range may partially or completely coincide with either the first frequency range or the second frequency range, whichever is further from the third frequency filter in the signal transmission direction. The frequency range outside the third frequency range may be complementary to the third frequency range so that all signals having frequencies outside the third frequency range are blocked and all signals having frequencies within the third frequency range are transmitted.

[0052] For the above purposes, the arrangement 200 also includes at least one additional frequency converter, the second frequency converter 230, coupled between the device and the third frequency filters 210, 220. The coupling may be configured such that, in response to an input signal having an input frequency provided to the device, the arrangement generates an output signal from the third frequency filter having an output frequency substantially corresponding to the input frequency, or such that, in response to an input signal having an input frequency provided to the third frequency filter, the arrangement generates an output signal from the device having an output frequency substantially corresponding to the input frequency. The second frequency converter may mirror or substantially mirror the (first) frequency converter for frequency conversion, at least with respect to the converted frequency value. The (first) frequency converter and the second frequency converter may be similar, identical, or different, except for the fact that they perform frequency conversion in opposite directions. Like the (first) frequency converter 130, the second frequency converter also has a mirror or substantially mirror function with respect to signal transmission between its first input / output and second input / output. irreversible In particular, the second frequency converter may be configured to prioritize signal transmission in the same direction as the (first) frequency converter. irreversibleThe characteristic may be responsive to an external drive signal to or for the second frequency converter. The arrangement may be configured to automatically provide the external drive signal. This may be provided simultaneously or separately with respect to the external drive signal to or for the (first) frequency converter. The (first) frequency converter and the second frequency converter may also share an external drive signal. The second frequency converter 230 may comprise or consist of one or more TWPAs. Alternatively or additionally, it may comprise or consist of one or more tunable phase shifters and / or Josephson parametric converters.

[0053] The third frequency filters 210, 220 and the second frequency converter 230 may be coupled before or after the device 100. In either case, the second frequency converter may be coupled between the third frequency filter and the device. With respect to the device 100, the arrangement 200 may be configured to have a forward direction for signal transmission from the first frequency filter to the second frequency filter or from the second frequency filter to the first frequency filter. In either case, the third frequency filter may be before or after the first and second frequency filters, thereby providing four possible arrangements of the arrangement. The arrangement and corresponding method may have any of the following four sequences: first filtering-(first) frequency translation-second filtering-second frequency translation-third filtering; second filtering-(first) frequency translation-first filtering-second frequency translation-third filtering; third filtering-second frequency translation-second filtering-(first) frequency translation-first filtering; and third filtering-second frequency translation-first filtering-(first) frequency translation-second filtering. Of these, Figure 2a shows the second example, and Figure 2b shows the third example. In each case, the (first) frequency translation is configured to prioritize forward signal transmission from the second frequency filter to the first frequency filter. A first example can be obtained from the arrangement of Figure 2b, where the signal source 10 is coupled to the opposite end of the arrangement, namely the first frequency filter 110, and the frequency translation in the (first) frequency converter is configured to prioritize forward signal transmission from the first frequency filter to the second frequency filter. A fourth example can be obtained from the arrangement of Figure 2a, where the signal source 10 is coupled to the opposite end of the arrangement, namely the third frequency filter 220, and the frequency translation in the (first) frequency converter is configured to prioritize forward signal transmission from the first frequency filter to the second frequency filter.

[0054] In the device 100, the first frequency filter 110 and / or the second frequency filter 120 may generally be passive filters. In particular, the first frequency filter 110 and / or the second frequency filter 120 may be implemented by a diplexer. However, instead of separating two frequency bands for further transmission, one of the bands may be blocked. The frequency filters may include one or more resistors for signal termination. The first filter and / or the second filter may be configured to appear as resistive filters in the circuit, for example, for all frequencies or for frequencies within any or all of a first low frequency range, a first high frequency range, a second low frequency range, a second high frequency range, a third frequency range, and a frequency range outside the third frequency range. For electromagnetic isolation, they may function as resistive filters with a resistance of, for example, 50 ohms ±0 to 10 ohms, 50 ohms ±0 to 2 ohms, or substantially 50 ohms. The reflection of the frequency filter, e.g., as represented by the reflection parameter (s11), may be smaller than the gain of the frequency converter in the forward direction, e.g., away from the signal source 10. All of the above also applies to the third frequency filters 210, 220.

[0055] The apparatus 100 and components may be configured to operate at cryogenic temperatures, which applies to any or all of the components disclosed herein, particularly the first frequency filter, the second frequency filter and the (first) frequency converter, and optionally the third frequency filter and / or the second frequency converter.

[0056] 3 illustrates an example method. Method 300 may include any of the acts described in connection with apparatus 100 and / or arrangement 200. The method may be used for electromagnetic isolation, e.g., isolating quantum computing circuitry, which may be at a cryogenic operating temperature, from electronic equipment, such as one or more amplifiers, that are at higher temperatures.

[0057] The method 300 includes facilitating first frequency filtering in a first frequency filter and facilitating second frequency filtering in a second frequency filter. The first filtering transmits signals having frequencies within a first low frequency range and blocks signals having frequencies within a first high frequency range. The second filtering blocks signals having frequencies within a second low frequency range and transmits signals having frequencies within a second high frequency range. The first and second frequency filtering may be frequency-mirrored relative to each other. The two filters may be performed in a serial configuration, with the first frequency filter in serial with the second frequency filter. Optionally, the method may include facilitating third frequency filtering in a third frequency filter. The third filtering may transmit signals having frequencies within a third frequency range and block signals having frequencies within a frequency range outside the third frequency range. As noted above, the third frequency range may partially or completely coincide with either the first or second frequency range, and in either case, what is said about either frequency range applies to the entire disclosure of the devices, structures, and methods.

[0058] Method 300 also includes facilitating a (first) frequency conversion between a first input / output coupled to the first frequency filter and a second input / output coupled to the second frequency filter. The frequency conversion may be performed by the (first) frequency converter 130, such that the first input / output is the first input / output 132 of the frequency converter and the second input / output is the second input / output of the frequency converter. The frequency conversion may be performed in a series configuration with respect to the two filters, such that the frequency conversion is performed between the first and second frequency filtering, and their relative order in the series configuration may be determined to mitigate backaction for electromagnetic isolation, for example, as shown in the context of apparatus 100 or structure 200. The frequency conversion may be performed in response to an external driving signal for the frequency conversion, for example, in relation to signal transmission between the first input / output terminal and the second input / output terminal, to relatively suppress or relatively enhance an output signal of the frequency conversion having a frequency within the first low frequency range at the first input / output terminal with respect to an output signal of the frequency conversion having a frequency within the second high frequency range at the second input / output terminal. irreversible The (first) frequency conversion can be performed in a time-domain manner, so that one-way signal transmission can be prioritized. irreversible This allows the method to be used for electromagnetic isolation, so that together with the first and second filtering, signal transmission from the signal source takes priority over signal transmission towards the signal source.

[0059] Optionally, when the method includes third frequency filtering, the method may also include a step of facilitating a second frequency conversion. This may be performed by the second frequency converter 230 and may involve any of the features described in connection with the second frequency converter. In particular, the second frequency conversion may mirror or substantially mirror the frequency conversion with respect to the (first) frequency conversion, at least with respect to the converted frequency values. The second frequency conversion may be performed in a serial configuration with respect to filtering, such that the third frequency filtering is performed between either the first frequency filtering or the second frequency filtering performed between the other two frequency filterings at 330. This allows the third frequency filtering to always be performed as the first 310 or the last 350 of the three serially configured frequency filterings. In the former case, the second frequency conversion is performed in a serial configuration before the first and second frequency filtering and the (first) frequency conversion, and in the latter case, the second frequency conversion is performed in a serial configuration after the first and second frequency filtering and the (first) frequency conversion.

[0060] Accordingly, the method can be performed such that, in response to performing first frequency filtering, (first) frequency translation, and second frequency filtering on an input signal having an input frequency, an output signal having an output frequency substantially corresponding to the input frequency is generated from the third frequency filter. This occurs in the second case described above. In the serial configuration, the input signal first undergoes first or second frequency filtering at 310, then (first) frequency translation at 320, then second or first frequency filtering (whichever has not already been performed) at 330, then second frequency translation at 340, and then third frequency filtering. In the forward direction of the electromagnetic isolation, this corresponds to transmitting the (first) signal, e.g., as a read signal, from a signal source to, e.g., a hotter processing stage. This allows the second frequency translation to correspond to an inverse frequency translation, while the most central frequency filtering 330 of the three frequency filtering 310, 330, 350 suppresses any or all non-transformed backaction signals or sub-signals from being transmitted across the two frequency translations 320, 340.

[0061] Alternatively, the method can be performed such that, in response to providing an input signal having an input frequency to the third frequency filter, an output signal having an output frequency substantially corresponding to the input frequency is generated from the first frequency filter or the second frequency filter. This occurs in the first case described above. In a serial configuration, the input signal first undergoes third frequency filtering at 310, then second frequency translation at 320, then first frequency filtering or second frequency filtering at 330, then (first) frequency translation at 340, then second frequency filtering or first frequency filtering, whichever has not already been performed. In the forward direction of electromagnetic isolation, this also corresponds to transmitting the (first) signal, e.g., as a read signal, from the signal source to, e.g., a hotter processing stage. Here, the first frequency transformation may correspond to an inverse frequency transformation, while the most central frequency filtering 330 of the three frequency filtering 310, 330, 350 suppresses any or all non-transformed backaction signals or sub-signals from being transmitted across the two frequency transformations 320, 340.

[0062] The method 300 may be performed at cryogenic temperatures. The method may be performed to mitigate or prevent backaction noise being transmitted to a signal source, for example, a quantum processing unit.

[0063] With respect to the apparatus 100, the arrangement 200, and the method 300, the TWPA is irreversibleThis has been found to provide particularly advantageous characteristics for frequency translation. In the case of a TWPA, the forward and reverse gains may differ. Also, the amplitudes of the reverse and forward idler signal generated across the TWPA may differ. The transmission spectrum of the TWPA's input and output filters can be separated into two frequency ranges, allowing the input and output filters to filter out the reverse signal, facilitating primary and secondary filtering. The TWPA can generate the forward idler signal without interference from the filters. The original signal at the input frequency can be filtered out by primary and / or secondary filtering. However, the same information can be transmitted by the idler signal, which can be used as an output signal to retrieve any or all information related to the input signal. Meanwhile, any reverse idler signal generated by the TWPA may be significantly attenuated.

[0064] Figures 4a, 4b, and 4c show an example simulation. In these examples, a simplified version of a TWPA is numerically simulated to demonstrate how the reverse idler signal of a TWPA can be attenuated under forward pumping. As can be seen in Figures 4a:420 and 4c, without pumping, the simulated circuit has near unity transmission in both the forward and reverse directions. Under pumping, the TWPA can be configured to transmit in the reverse direction to maintain unity, while the forward direction exhibits gain, as shown in Figure 4a:410. In Figure 4b:430, the signal without pumping is slightly offset in frequency so that it does not overlap with adjacent peaks corresponding to the signal with pumping, allowing amplitude changes to be more easily verified. In this figure, the highest peak corresponds to pumping and is therefore not part of the input / output signal characteristic.

[0065] The various functions described herein may be performed in different orders and / or concurrently with one another unless otherwise indicated.

[0066] The values ​​of any ranges or devices described herein may be expanded or modified without losing the effect sought, unless otherwise stated, and any example may be combined with another example, unless expressly prohibited.

[0067] Although the subject matter has been described in language specific to structural features and / or acts, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims, and other equivalent features and acts are intended to be within the scope of the claims.

[0068] It will be understood that the benefits and advantages described above may relate to one embodiment or several embodiments. The embodiments are not limited to those that solve any or all of the described problems or have any or all of the described benefits and advantages. Furthermore, it will be understood that references to "an" or "an" item may refer to one or more of those items.

[0069] As used herein, the term "comprising" is used to mean including the specified methods, blocks, or elements, but that such blocks or elements do not constitute an exclusive list, and that the method or apparatus may include additional blocks or elements.

[0070] Numerical descriptors such as "first," "second," etc. are used herein merely as a way of distinguishing between otherwise similarly named moieties, and are not to be construed as indicating any particular order, such as priority, order of production, or order of occurrence in any particular structure.

[0071] While the present invention has been described in connection with certain types of devices and / or methods, it should be understood that the present invention is not limited to any type of device and / or method. While the present invention has been described in connection with several examples, embodiments, and implementations, the present invention is not so limited, but rather covers various modifications and equivalent arrangements that fall within the scope of the appended claims. While various examples have been described above with a certain degree of particularity or with reference to one or more individual embodiments, those skilled in the art may make many modifications to the disclosed examples without departing from the scope of this specification. [Explanation of symbols]

[0072] 10 Signal source 20 signals 40 Threshold Frequency 100 devices 110 Frequency Filter 120 Frequency Filter 130 Frequency Converter 132 first input / output terminal 134 Second Input / Output Terminal 200 Constructs 210 Third Frequency Filter 220 Third Frequency Filter 230 Second frequency converter 300 ways 310 Frequency Filtering 320 Frequency Conversion 330 Frequency Filtering 340 Frequency Conversion 350 Frequency Filtering

Claims

1. 1. An apparatus for electromagnetic isolation of a quantum computing circuit, comprising: a first frequency filter configured to transmit signals having frequencies within a first low frequency range and to block signals having frequencies within a first high frequency range; a second frequency filter configured to block signals having frequencies within a second low frequency range and to transmit signals having frequencies within a second high frequency range; a frequency converter having a first input / output coupled to the first frequency filter and a second input / output coupled to the second frequency filter, a frequency converter configured to be non-reciprocal with respect to signal transmission between the first input / output and the second input / output in response to an external drive signal to the frequency converter, so as to relatively suppress or relatively enhance an output signal of the frequency converter at the first input / output of the frequency converter having a frequency within the first low frequency range with respect to an output signal of the frequency converter at the second input / output of the frequency converter having a frequency within the second high frequency range; An apparatus comprising:

2. 2. The apparatus of claim 1, wherein in response to the external drive signal, the frequency converter is configured to generate gain for its output signal having a frequency within the second high frequency range at the second input / output end of the frequency converter and / or generate attenuation for its output signal having a frequency within the first low frequency range at the first input / output end of the frequency converter.

3. 2. The apparatus of claim 1, wherein, in response to the external drive signal, the frequency converter is configured to generate gain for its output signal having a frequency within the first low frequency range at the first input / output end of the frequency converter and / or generate attenuation for its output signal having a frequency within the second high frequency range at the second input / output end of the frequency converter.

4. 4. The apparatus of claim 1, wherein the frequency converter is a traveling wave parametric amplifier.

5. 4. The device according to claim 1, wherein the frequency converter is a tunable phase shifter and / or a Josephson parametric converter.

6. 6. The device according to claim 1, wherein the first frequency filter and / or the second frequency filter are passive filters.

7. 7. The apparatus of claim 1, wherein the first low frequency range corresponds to the second low frequency range and / or the first high frequency range corresponds to the second high frequency range.

8. A construct comprising: A device according to any one of claims 1 to 7; a third frequency filter configured to transmit signals having frequencies within a third frequency range and to block signals having frequencies within a frequency range outside the third frequency range; a second frequency converter, wherein in response to an input signal having an input frequency provided to the apparatus, the arrangement is configured to generate an output signal from the third frequency filter having an output frequency substantially corresponding to the input frequency; or In response to an input signal having an input frequency provided to the third frequency filter, the arrangement is configured to generate an output signal from the device having an output frequency substantially corresponding to the input frequency. a second frequency converter coupled between the device and the third frequency filter such that A construct that includes:

9. 9. An arrangement comprising one or more devices according to any one of claims 1 to 7 and / or a quantum processing unit coupled to an arrangement according to claim 8 to prevent backaction noise to the quantum processing unit.

10. 1. A method for electromagnetic isolation of a quantum computing circuit, comprising: facilitating frequency filtering in a first frequency filter, wherein signals having frequencies within a first low frequency range are transmitted and signals having frequencies within a first high frequency range are blocked; facilitating frequency filtering in a second frequency filter, wherein signals having frequencies within a second low frequency range are blocked and signals having frequencies within a second high frequency range are transmitted; facilitating a frequency conversion between a first input / output coupled to the first frequency filter and a second input / output coupled to the second frequency filter, the frequency conversion being non-reciprocal with respect to signal transmission between the first input / output and the second input / output in response to an external drive signal for the frequency conversion to relatively suppress or relatively enhance an output signal of the frequency conversion at the first input / output having a frequency within the first low frequency range relative to an output signal of the frequency conversion at the second input / output having a frequency within the second high frequency range; A method comprising:

11. 11. The method of claim 10, wherein, in response to the external drive signal, the frequency conversion generates gain for its output signal at the second input / output end having a frequency within the second high frequency range and / or generates attenuation for its output signal at the first input / output end having a frequency within the first low frequency range.

12. 11. The method of claim 10, wherein, in response to the external drive signal, the frequency conversion generates gain for its output signal having a frequency within the first low frequency range at the first input / output end and / or generates attenuation for its output signal having a frequency within the second high frequency range at the second input / output end.

13. 13. The method of any one of claims 10 to 12, wherein the frequency conversion is facilitated by a traveling wave parametric amplifier.

14. 13. The method of any one of claims 10 to 12, wherein the frequency conversion is facilitated by a tunable phase shifter and / or a Josephson parametric converter.

15. 15. The method according to any one of claims 10 to 14, wherein the frequency filtering in the first frequency filter and / or the second frequency filter is performed passively.

16. 16. The method of claim 10, wherein the first low frequency range corresponds to the second low frequency range and / or the first high frequency range corresponds to the second high frequency range.

17. Executing a first method according to any one of claims 10 to 16; facilitating frequency filtering in a third frequency filter, wherein signals having frequencies within a third frequency range are transmitted and signals having frequencies within a frequency range outside the third frequency range are blocked; In response to performing the first method on an input signal having an input frequency, an output signal is produced from the third frequency filter having an output frequency that substantially corresponds to the input frequency; or In response to providing an input signal having an input frequency to the third frequency filter, an output signal having an output frequency substantially corresponding to the input frequency is generated from the first frequency filter or the second frequency filter. facilitating a second frequency translation between frequency filtering in the third frequency filter and frequency filtering in the first frequency filter or the second frequency filter, such that A method comprising:

18. 18. The method of any one of claims 10 to 17, performed to prevent backaction noise to a quantum processing unit.

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