# US 10,311,379 B1 · Isolation of frequency multiplexed microwave signals using cascading multi-path interferometric josephson isolators with nonoverlapping bandwidths > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,311,379 B1 - Document ID: US10311379B1 - Status: Granted - Kind: B1 - Application number: 15/829,054 - Filed: 2017-12-01 - Published: 2019-06-06 - Granted: 2019-06-04 - Earliest claimed: 2017-12-01 - Assignees: International Business Machines Corporation - Applicants: International Business Machines Corporation - Inventors: Baleegh Abdo - Web page: https://patentgrep.com/patent/US10311379B1 ## CPC - H03K 17/92: by the use, as active elements, of superconductive devices - H03K 3/38: by the use, as active elements, of superconductive devices - H04J 1/02: Details - H04J 2203/00: Aspects of optical multiplex systems other than those covered by H04J14/05 and H04J14/07 - H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M) - H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S) ## Abstract A cascading microwave isolator (cascade) includes a set of Josephson devices, each Josephson device in the set having a corresponding operating bandwidth of microwave frequencies. Different operating bandwidths have different corresponding center frequencies. A series coupling is formed between first Josephson device from the set and an nth Josephson device from the set. The series coupling causes the first Josephson device to isolate a signal at a first frequency from a frequency multiplexed microwave signal (multiplexed signal) in a first signal flow direction through the series coupling and the nth Josephson device to isolate a signal at an nth frequency from the multiplexed signal in the first signal flow direction through the series. ## Claims ### Claim 1 A cascading microwave isolator (cascade) comprising: a set of Josephson devices, each Josephson device in the set having a corresponding operating bandwidth of microwave frequencies, wherein different operating bandwidths have different corresponding center frequencies; and a series coupling between first Josephson device from the set and an nth Josephson device from the set, wherein the series coupling causes the first Josephson device to isolate a signal at a first frequency from a frequency multiplexed microwave signal (multiplexed signal) in a first signal flow direction through the series coupling and the nth Josephson device to isolate a signal at an nth frequency from the multiplexed signal in the first signal flow direction through the series. ### Claim 2 (depends on 1) The cascade of claim 1, further comprising: an (n−1)th Josephson device from the set in the series coupling, wherein n is greater than 1, wherein the (n−1)th Josephson device is included the series coupling between the first Josephson device and the nth Josephson device, and wherein the (n−1)th Josephson device isolates a signal at an (n−1)th frequency from the multiplexed signal in the first signal flow direction. ### Claim 3 (depends on 1) The cascade of claim 1, wherein the series coupling causes the first Josephson device to propagate the signal at an nth frequency from the multiplexed signal in the first signal flow direction through the series coupling and the nth Josephson device to propagate the signal at the first frequency in the first signal flow direction through the series. ### Claim 4 (depends on 1) The cascade of claim 1, wherein the series coupling causes the first Josephson device and the nth Josephson device to propagate all signals at frequencies from the multiplexed signal in a second signal flow direction through the series coupling, wherein the second signal flow direction is opposite of the first signal flow direction, and wherein the first signal flow direction is a direction of isolation of the first Josephson device and the nth Josephson device. ### Claim 5 (depends on 1) The cascade of claim 1, wherein a first operating bandwidth of microwave frequencies corresponding to the first Josephson device is nonoverlapping for at least some frequencies with an nth operating bandwidth of microwave frequencies corresponding to the nth Josephson device. ### Claim 6 (depends on 5) The cascade of claim 5, wherein a total isolation bandwidth of the cascade comprises the first operating bandwidth and the nth operating bandwidth. ### Claim 7 (depends on 1) The cascade of claim 1, wherein the first Josephson device in the set of Josephson devices is an MPIJIS, comprises: a first nondegenerate microwave mixer device (first mixer); a second nondegenerate microwave mixer device (second mixer); a first input/output (I/O) port coupled to an input port of the first mixer and an input port of the second mixer; and a second I/O port coupled to the input port of the first mixer and the input port of the second mixer, wherein the signal of the first frequency communicated between the first I/O port and the second I/O port is transmitted while propagating in a first direction between the first I/O port to the second I/O port through the first mixer and the second mixer and is blocked while propagating in a second direction between the second I/O port to the first I/O through the first mixer and the second mixer, and wherein the first frequency is in a first operating bandwidth of the first Josephson device. ### Claim 8 (depends on 7) The cascade of claim 7, further comprising: a first microwave pump injecting a first microwave drive into the first mixer at a pump frequency and a first pump phase, wherein the first microwave pump is configured to cause the first mixer to operate at a 50:50 beamsplitting working point; and a second microwave pump injecting a second microwave drive into the second mixer at the pump frequency and a second pump phase wherein the second microwave pump is configured to cause the second mixer to operate at the 50:50 beamsplitting working point, and wherein a phase difference between the first pump phase and the second pump phase determines an isolation direction. ### Claim 9 (depends on 7) The cascade of claim 7, wherein the first mixer and the second mixer are each a nondegenerate three-wave mixer. ### Claim 10 (depends on 7) The cascade of claim 7, wherein the first mixer and the second mixer are each a Josephson parametric converter (JPC), and wherein the first mixer and the second mixer are nominally identical. ### Claim 11 A method to form a cascading microwave isolator (cascade), the method comprising: fabricating a set of Josephson devices, each Josephson device in the set having a corresponding operating bandwidth of microwave frequencies, wherein different operating bandwidths have different corresponding center frequencies; and forming a series coupling between first Josephson device from the set and an nth Josephson device from the set, wherein the series coupling causes the first Josephson device to isolate a signal at a first frequency from a frequency multiplexed microwave signal (multiplexed signal) in a first signal flow direction through the series coupling and the nth Josephson device to isolate a signal at an nth frequency from the multiplexed signal in the first signal flow direction through the series. ### Claim 12 A superconductor fabrication system which when operated to fabricate a cascading microwave isolator (cascade) performing operations comprising: fabricating a set of Josephson devices, each Josephson device in the set having a corresponding operating bandwidth of microwave frequencies, wherein different operating bandwidths have different corresponding center frequencies; and forming a series coupling between first Josephson device from the set and an nth Josephson device from the set, wherein the series coupling causes the first Josephson device to isolate a signal at a first frequency from a frequency multiplexed microwave signal (multiplexed signal) in a first signal flow direction through the series coupling and the nth Josephson device to isolate a signal at an nth frequency from the multiplexed signal in the first signal flow direction through the series. ### Claim 13 (depends on 12) The superconductor fabrication system of claim 12, further comprising: an (n−1)th Josephson device from the set in the series coupling, wherein n is greater than 1, wherein the (n−1)th Josephson device is included the series coupling between the first Josephson device and the nth Josephson device, and wherein the (n−1)th Josephson device isolates a signal at an (n−1)th frequency from the multiplexed signal in the first signal flow direction. ### Claim 14 (depends on 12) The superconductor fabrication system of claim 12, wherein the series coupling causes the first Josephson device to propagate the signal at an nth frequency from the multiplexed signal in the first signal flow direction through the series coupling and the nth Josephson device to propagate the signal at the first frequency in the first signal flow direction through the series. ### Claim 15 (depends on 12) The superconductor fabrication system of claim 12, wherein the series coupling causes the first Josephson device and the nth Josephson device to propagate all signals at frequencies from the multiplexed signal in a second signal flow direction through the series coupling, wherein the second signal flow direction is opposite of the first signal flow direction, and wherein the first signal flow direction is a direction of isolation of the first Josephson device and the nth Josephson device. ### Claim 16 (depends on 12) The superconductor fabrication system of claim 12, wherein a first operating bandwidth of microwave frequencies corresponding to the first Josephson device is nonoverlapping for at least some frequencies with an nth operating bandwidth of microwave frequencies corresponding to the nth Josephson device. ### Claim 17 (depends on 16) The superconductor fabrication system of claim 16, wherein a total isolation bandwidth of the cascade comprises the first operating bandwidth and the nth operating bandwidth. ### Claim 18 (depends on 12) The superconductor fabrication system of claim 12, wherein the first Josephson device in the set of Josephson devices is an MPIJIS, comprises: a first nondegenerate microwave mixer device (first mixer); a second nondegenerate microwave mixer device (second mixer); a first input/output (I/O) port coupled to an input port of the first mixer and an input port of the second mixer; and a second I/O port coupled to the input port of the first mixer and the input port of the second mixer, wherein the signal of the first frequency communicated between the first I/O port and the second I/O port is transmitted while propagating in a first direction between the first I/O port to the second I/O port through the first mixer and the second mixer and is blocked while propagating in a second direction between the second I/O port to the first I/O through the first mixer and the second mixer, and wherein the first frequency is in a first operating bandwidth of the first Josephson device. ### Claim 19 (depends on 18) The superconductor fabrication system of claim 18, further comprising: a first microwave pump injecting a first microwave drive into the first mixer at a pump frequency and a first pump phase, wherein the first microwave pump is configured to cause the first mixer to operate at a 50:50 beamsplitting working point; and a second microwave pump injecting a second microwave drive into the second mixer at the pump frequency and a second pump phase wherein the second microwave pump is configured to cause the second mixer to operate at the 50:50 beamsplitting working point, and wherein a phase difference between the first pump phase and the second pump phase determines an isolation direction. ### Claim 20 (depends on 18) The superconductor fabrication system of claim 18, wherein the first mixer and the second mixer are each a nondegenerate three-wave mixer.