# US 12,763,448 B2 · Multi-resonator random access quantum memory with integrated magnet-less circulator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,763,448 B2 - Document ID: US12763448B2 - Status: Granted - Kind: B2 - Application number: 18/967,616 - Filed: 2024-12-03 - Published: 2026-06-18 - Granted: 2026-10-13 - Earliest claimed: 2024-12-03 - Assignees: Dell Products L.P. - Applicants: Dell Products L.P. - Inventors: Tejinder Singh; Navjot Kaur Khaira - Web page: https://patentgrep.com/patent/US12763448B2 ## CPC - H01P 1/38: Circulators - H03H 9/725: {Duplexers} - H01P: WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE (operating at optical frequencies G02B) - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) ## Abstract The technology described herein is directed towards a multi-bit random-access quantum memory (RAQM) system based on reconfigurable tunable resonators. The RAQM system includes an array of (e.g., four) tunable high-Q resonators which, when one is tuned to the same frequency as a common (shared) broadband tunable low quality resonator, strongly interact to write a qubit to the high-Q resonators, and similarly readout a previously stored qubit. The shared low-Q and multiple high-Q resonators can be fabricated in a monolithically-integrated stack, without consuming a large circuit footprint or chip area. The low-Q resonator can be coupled to an external feed-line to obtain the qubits through a circulator, facilitating efficient read/write operations from and to the quantum memory storage portion of the RAQM system. In one implementation, the circulator is a magnet-less circulator, facilitating deployment of the RAQM system at cryogenic temperatures. ## Claims ### Claim 1 A system, comprising: a group of respective quantum memory cells, comprising respective resonators coupled to a shared resonator; and a superconducting magnet-less circulator device, comprising a first circulator port, a second circulator port coupled to the shared resonator, and a third circulator port, wherein a quantum bit obtained at the first circulator port is routed to the second circulator port, and wherein the shared resonator resonates at a first frequency, and one of the respective resonators comprises a selected resonator tuned to resonate at the first frequency, to transfer the quantum bit from the second circulator port, via the shared resonator, to the selected resonator, and detuned to store the quantum bit in the selected resonator and prevent transfer of the quantum bit from the selected resonator back to the second circulator port, via the shared resonator. ### Claim 2 (depends on 1) The system of claim 1, wherein the shared resonator and the selected resonator are retuned to resonate at the first frequency to transfer the quantum bit as stored in the selected resonator back to the second circulator port via the shared resonator, and routed from the second circulator port to the third circulator port for readout. ### Claim 3 (depends on 1) The system of claim 1, wherein the quantum bit obtained at the first circulator port is a first quantum bit obtained at a first time, wherein the selected resonator is a first selected resonator, and wherein a second quantum bit obtained at the first circulator port at a second time is routed to the second circulator port, wherein the shared resonator resonates at a second frequency, and one of the respective resonators other than the first selected resonator comprises a second selected resonator tuned to resonate at the second frequency, to transfer the second quantum bit from the second circulator port, via the shared resonator, to the second selected resonator, and detuned to store the second quantum bit in the second selected resonator and prevent transfer of the second quantum bit from the second selected resonator back to the second circulator port, via the shared resonator. ### Claim 4 (depends on 3) The system of claim 3, wherein the shared resonator and the second selected resonator are retuned to resonate at the second frequency to transfer the second quantum bit as stored in the second selected resonator back to the second circulator port via the shared resonator, and routed from the second circulator port to the third circulator port for readout. ### Claim 5 (depends on 1) The system of claim 1, wherein the shared resonator comprises a relatively low quality factor resonator. ### Claim 6 (depends on 1) The system of claim 1, wherein the shared resonator comprises an interdigitated capacitor and a microstrip inductor tuned by one or more radio frequency-superconducting quantum interference devices. ### Claim 7 (depends on 1) The system of claim 1, wherein the respective resonators comprise respective relatively high quality factor resonators. ### Claim 8 (depends on 1) The system of claim 1, wherein the respective resonators comprise respective multi-stacked capacitors coupled to respective inductors tuned by respective radio frequency-superconducting quantum interference device groupings. ### Claim 9 (depends on 1) The system of claim 1, wherein the superconducting magnet-less circulator device comprises a first tank circuit, a second tank circuit and a third tank circuit, wherein the first tank circuit resonates out of phase with the second tank circuit and the third tank circuit, and wherein the second tank circuit resonates out of phase with the third tank circuit. ### Claim 10 (depends on 9) The system of claim 9, wherein the first circulator port is coupled to the first tank circuit, the first tank circuit comprising a first inductor and a first capacitor resonating at a first resonant frequency, as controlled by a first modulated microwave frequency control signal coupled to a first radio frequency-superconducting quantum interference device (rf-SQUID) set inductively coupled to the first tank circuit, wherein the second circulator port is coupled to the second tank circuit, the second tank circuit comprising a second inductor and a second capacitor resonating at a second resonant frequency as controlled by a second modulated microwave frequency control signal coupled to a second rf-SQUID set inductively coupled to the second tank circuit, wherein the third circulator port is coupled to the third tank circuit, the third tank circuit comprising a third inductor and a third capacitor resonating at a third resonant frequency as controlled by a third modulated microwave frequency control signal coupled to a third rf-SQUID set inductively coupled to the third tank circuit, and wherein, for an input signal obtained at the first circulator port, the first resonant frequency and the second resonant frequency interfere constructively to facilitate a flow of the first input signal to the second circulator port, and the first resonant frequency and the third resonant frequency interfere destructively to impede the flow of the first input signal to the third circulator port. ### Claim 11 A method, comprising: routing, by a system comprising at least one processor, a quantum bit obtained at a first circulator port of a magnet-less circulator device to a second circulator port of the magnet-less circulator device, in conjunction with impeding the qubit signal flow from the first circulator port to a third circulator port of the magnet-less circulator device; resonating, by the system, a shared resonator and a tunable resonator at a common frequency, wherein the shared resonator is coupled to the second circulator port, to transfer the quantum bit from the second circulator port, via the shared resonator, to the tunable resonator; and resonating, by the system, the shared resonator and the tunable resonator at different frequencies from one another to store the quantum bit in the tunable resonator and prevent transfer of the quantum bit from the tunable resonator back to the second circulator port via the shared resonator. ### Claim 12 (depends on 11) The method of claim 11, further comprising resonating, by the system, the shared resonator and the tunable resonator at the common frequency, to transfer the quantum bit as stored in the tunable resonator back to the second port via the shared resonator for output by the system. ### Claim 13 (depends on 12) The method of claim 12, further comprising routing, by the system, the quantum bit to the third port, and reading, by the system, the quantum bit from the third port. ### Claim 14 (depends on 11) The method of claim 11, wherein the shared resonator is tunable, and wherein the resonating of the shared resonator at the common frequency comprises tuning the shared resonator to the common frequency. ### Claim 15 (depends on 11) The method of claim 11, wherein the resonating of the tunable resonator at the common frequency comprises tuning the tunable resonator to the common frequency. ### Claim 16 (depends on 11) The method of claim 11, wherein the quantum bit comprises a first quantum bit obtained at a first time, wherein the tunable resonator is a first tunable resonator, wherein the common frequency is a first common frequency, wherein the different frequencies are first different frequencies, and further comprising: routing, by the system, a second quantum bit obtained at the first circulator port at a second time, resonating, by the system, the shared resonator and a second tunable resonator at a second common frequency, wherein the second shared resonator is coupled to the second circulator port, to transfer the second quantum bit from the second circulator port, via the shared resonator, to the second tunable resonator; resonating, by the system, the shared resonator and the second tunable resonator at second different frequencies from one another to store the quantum bit in the second tunable resonator and prevent transfer of the second quantum bit from the second tunable resonator back to the second circulator port via the shared resonator; routing, by the system, a third quantum bit obtained at the first circulator port at a third time, resonating, by the system, the shared resonator and a third tunable resonator at a third common frequency, wherein the third shared resonator is coupled to the second circulator port, to transfer the third quantum bit from the second circulator port, via the shared resonator, to the third tunable resonator; resonating, by the system, the shared resonator and the third tunable resonator at third different frequencies from one another to store the quantum bit in the third tunable resonator and prevent transfer of the third quantum bit from the third tunable resonator back to the second circulator port via the shared resonator; routing, by the system, a fourth quantum bit obtained at the first circulator port at a fourth time, resonating, by the system, the shared resonator and a fourth tunable resonator at a fourth common frequency, wherein the fourth shared resonator is coupled to the second circulator port, to transfer the fourth quantum bit from the second circulator port, via the shared resonator, to the fourth tunable resonator; and resonating, by the system, the shared resonator and the fourth tunable resonator at fourth different frequencies from one another to store the fourth quantum bit in the fourth tunable resonator and prevent transfer of the fourth quantum bit from the fourth tunable resonator back to the second circulator port via the shared resonator. ### Claim 17 A system, comprising: a group of respective quantum memory cells, comprising respective resonators coupled to a shared resonator; and a superconducting magnet-less circulator device, comprising a first circulator port, a second circulator port coupled to the shared resonator, and a third circulator port, wherein respective quantum bits obtained at the first circulator port at respective different times are routed to the second circulator port, wherein the respective resonators are tuned via respective radio frequency-superconducting quantum interference device (rf-SQUID) groupings coupled to the respective resonators, to respectively resonate at respective different frequencies at the respective different times to transfer the respective quantum bits from the second circulator port, via the shared resonator, to the respective resonators, and are respectively detuned to respectively store the respective quantum bits in the respective resonators and respectively prevent transfer of the respective quantum bits from the respective resonators back to the second circulator port, via the shared resonator. ### Claim 18 (depends on 17) The system of claim 17, wherein the shared resonator is tunable based on one or more other rf-SQUIDS coupled to the shared resonator. ### Claim 19 (depends on 17) The system of claim 17, wherein the respective resonators comprises four total relatively high quality factor resonators, and wherein the shared resonator comprises a single relatively low quality factor resonator. ### Claim 20 (depends on 17) The system of claim 17, wherein the superconducting magnet-less circulator device comprises a first tank circuit coupled to the first circulator port, a second tank circuit coupled to the second circulator port, and a third tank circuit coupled to the third circulator port, wherein respective resonations of the first tank circuit, of the second tank circuit, and the third tank circuit result in an electronic angular momentum being imparted to the magnet-less circulator device, and wherein the electronic angular momentum being imparted to the magnet-less circulator device results in constructive interference of a first resonance frequency of the tank circuit and a second resonance frequency of the second tank circuit that routes the qubit signal flow from the first circulator port to the second circulator port, and further results in destructive interference of the first frequency and a third frequency of the third tank circuit that impedes the qubit signal flow from the first circulator port to the third circulator port.