Small volume uhm ion trap package and method of forming

Abstract

Aspects of the present disclosure describe systems, methods, and structures that implement compact UHV ion trap systems that can operate at temperatures higher than cryogenic temperatures. Ion trap systems according to the present disclosure are surface treated and sealed while held in a UHV environment, with different components joined via UHV seals, such as welded joints, compressible metal flanges, and UHV compatible welded joints. As a result, no cryogenic pumps are needed, thereby enabling a very small volume system.

Description

[0001] Statement as to Federally Sponsored Research

[0002] This application was made with government support under Federal Grant No. W911NF16-1-0082 awarded by the Army Research Office. The government has certain rights in the application.

[0003] Cross Reference to Related Applications

[0004] This application is a continuation-in-part of co-pending U.S. Non-Provisional Application No. 16 / 913,932, filed June 26, 2020 (Attorney Docket No. 525-015US2), which is a continuation of U.S. Non-Provisional Patent Application No. 15 / 935,312, filed March 26, 2018, now U.S. Patent No. 10,755,913 (Attorney Docket No. 525-015US1), which claims the benefit of U.S. Provisional Application No. 62 / 533,927, filed July 18, 2017 (Attorney Docket No. DU5308PROV), each of which is incorporated by reference as if set forth in detail herein.

[0005] This application also claims the benefit of U.S. Provisional Patent Application No. 63 / 049,842, filed July 9, 2020 (Attorney Docket No. DU7191PROV), which is incorporated by reference as if set forth in detail herein. TECHNICAL FIELD

[0006] The present disclosure relates generally to quantum computing and more specifically, to enclosures for ion traps capable of supporting ultra-high vacuum environments. BACKGROUND

[0007] Systems using atomic ions are one of the leading physical platforms for practical quantum computers due to their long coherence times, all-to-all connectivity between qubits, and high-fidelity gate operations. However, unlike solid-state based qubits, the integration approach for scaling trapped ion systems is not obvious. To establish a practical trapped ion quantum computing system, a number of novel ideas for designing complex trapped ion systems have been outlined.

[0008] Trapped ion experiments, whether they use traditional linear Paul traps or microfabricated surface traps, ultimately rely on the lack of collision events with background gas molecules in order to provide better qubit isolation and perform reliable high-fidelity gates. Crucially, it is required to be in an ultra-high vacuum (UHV) regime (<1*10 -11The pressure of the background gas collision rate is kept low enough to minimize ion chain reordering events and ion loss from the trap. In addition, quantum computing requires high-fidelity gates, which necessitates excellent optomechanical robustness and stability of the scalable trapped-ion quantum computer. The optical frequencies of the lasers driving near-resonant processes should be stabilized to the 10 10 Quantum logic gates typically use Raman transitions, where two far-detuned counter-propagating beams with precise frequency difference intersect at the ion location. Fluctuations in beam path length and pointing of these Raman beams result in fluctuations in the optical phase and intensity at the ion, which leads to imperfect gates. To avoid these problems, the trapped-ion system and optical elements used to deliver the laser beams should be kept stable from environmental noise such as temperature fluctuations, gas flow, and mechanical vibrations.

[0009] In the prior art, the requirements of a scalable trapped-ion quantum computer have been met by employing a cryogenic system, where the volume of the UHV operating region is kept small by maintaining its vacuum quality at low temperature at the same time. Unfortunately, cryogenic systems are bulky and expensive. In addition, closed-loop cryostats induce unwanted vibrations.

[0010] A practical compact trapped-ion system that does not require cryogenic operation would represent a step forward over the state of the art. SUMMARY

[0011] The present disclosure enables an extremely compact ion-trap system that can operate in ultra-high vacuum at non-cryogenic temperatures and can have a system volume of less than or equal to 10 cubic centimeters (cc).

[0012] The step forward over the prior art is achieved by performing in-situ surface treatment and vacuum sealing of the ion-trap enclosure of an ion-trap system while the ion-trap enclosure is maintained in an ultra-high vacuum (UHV) environment. Thus, the parts that make up the enclosure are joined using only UHV seals, such as welded joints, vacuum flanges, and UHV-compatible solder seals. Furthermore, embodiments according to the present disclosure do not include vacuum valves or pinch tubes, which are typically used in ion-trap enclosures of the prior art and are known to be bulky or unreliable over time. Also furthermore, by establishing a UHV environment before sealing the ion trap in the enclosure, the need for a large, complex cryogenic vacuum system is avoided, thereby enabling a very small volume ion-trap system.

[0013] An illustrative embodiment according to the present disclosure is an ion-trap system that includes an ion-trap enclosed in an enclosure having an approximate 2 cm 3an enclosure in a high vacuum chamber of volume. The enclosure includes a plurality of components including a chip carrier having an ion trap mounted thereon, a housing, and a lid, wherein each joint between components of the enclosure is made using a UHV seal, the UHV seal being positioned in a vacuum environment having a pressure less than or equal to 10 -9 torr. The enclosure is adapted for use in a UHV deposition system when the enclosure is sealed in the UHV environment. Because the enclosure is sealed while in an ultra-high vacuum state to establish its baseline pressure, the ion trap system is free of cryogenic cooling systems. Thus, the chamber and overall system can have a very small volume and the ion trap can operate at temperatures higher than cryogenic temperatures. In some embodiments, the enclosure is fluidly coupled with a vacuum pump prior to being sealed in the UHV environment such that the vacuum pump can further reduce the pressure in the chamber to well below 10 -10 torr.

[0014] In some embodiments, the enclosure includes one or more windows for providing a viewing port, an optical entrance for a photoionization laser signal to load ions into the ion trap, an optical entrance for a laser signal to ablate material to generate an atomic flux within the chamber, providing one or more laser signals to initialize, manipulate, and read out trapped ion qubits and / or collect scattered photons from trapped ion qubits for imaging and qubit state detection.

[0015] An embodiment according to the present disclosure is an ion trap system comprising: an ion trap disposed on a chip carrier; and an enclosure enclosing the ion trap in a first chamber, wherein the enclosure includes a plurality of components including the chip carrier and a housing, and wherein the components of the plurality of components are joined by a plurality of seals consisting of UHV seals; wherein the first chamber has a pressure less than or equal to 10 -10 torr; wherein the first chamber has an internal volume less than or equal to 10 cm 3 ; and wherein the ion trap system has an operating temperature greater than or equal to -50°C

[0016] Another embodiment according to the present disclosure is an ion trap system comprising: an ion trap disposed on a chip carrier; and an enclosure enclosing the ion trap in a first chamber, wherein the enclosure includes a plurality of components including the chip carrier and a housing; a plurality of seals consisting of UHV seals, wherein the plurality of seals join the components of the plurality of components; and an ion pump joined with the enclosure via a first UHV seal; wherein the first chamber has a pressure less than or equal to 10 -10a pressure of the first environment; wherein the ion trap is positioned within a chamber of an enclosure, the enclosure including a plurality of components linked with a plurality of seals consisting of UHV seals, the chamber open to the first environment; and forming a first UHV seal to isolate the chamber from the first environment while the ion trap and enclosure are positioned in the first environment.

[0017] Yet another embodiment in accordance with the present disclosure is a method for forming an ion trap system, the method comprising: positioning an ion trap in a first environment having a first pressure less than or equal to 10 -9 a pressure of the first environment; wherein the ion trap is positioned within a chamber of an enclosure, the enclosure including a plurality of components linked with a plurality of seals consisting of UHV seals, the chamber open to the first environment; and forming a first UHV seal to isolate the chamber from the first environment while the ion trap and enclosure are positioned in the first environment. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 A block diagram showing an illustrative ion trap system in accordance with the present disclosure is shown.

[0019] Figure 2A A schematic diagram depicting a top view and a cross-sectional view of an ion trap package in accordance with an illustrative embodiment is shown.

[0020] Figure 3 Operations of a method for forming an ion trap package in accordance with an illustrative embodiment are depicted.

[0021] Figure 4 A block diagram depicting a UHV assembly system in accordance with the present disclosure is shown.

[0022] Figure 5 Operations of a method for monitoring pressure inside an ion trap system in accordance with the present disclosure are depicted.

[0023] Figure 6A A simulation of a dual-well potential in accordance with the present disclosure is depicted.

[0024] Figure 6B A graph depicting the position of trapped ions between wells of a dual-well potential as a function of time in accordance with the present disclosure is depicted.

[0025] Figure 7 Operations of an alternative method for monitoring pressure inside an ion trap system in accordance with the present disclosure are depicted.

[0026] Figure 8A First and second chain configurations used to estimate collision energy of a six-ion chain of the method 700 are depicted.

[0027] Figure 8B A histogram depicting time intervals between ion reordering events is depicted. DETAILED DESCRIPTION

[0028] The following detailed description merely sets forth principles of the disclosure and a few, but not all, exemplary implementations thereof. This description and the representations herein are not intended to limit the scope of the disclosure, as such could be read to limit the scope in any way. Rather, the description and representations herein serve merely as teaching aids in setting forth a few of many implementations of the principles of the disclosure and thus provide details for the best enabling practice for one of ordinary skill in the art to which this disclosure pertains. The disclosure is defined only by the claims.

[0029] Furthermore, to the extent that the terms "comprises", "comprising", "includes", "including" and "has" or any variation thereof are used in the following detailed description and claims, these terms are intended to be inclusive in a manner similar to the term "comprising" as "comprising" is interpreted when employed as a transitional term in a claim.

[0030] Also, all statements regarding the examples, and embodiments of the disclosure herein are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future that perform the same function, regardless of structure. The scope of the present disclosure, therefore, is not intended to be limited to the examples shown herein but is to be accorded the full scope consistent with the scope of the claims, wherein reference to an

[0031] Thus, for example, any flow diagrams, flow charts, data flow diagrams, sequence diagrams, state transition diagrams, pseudocode, and the like represent various processes which can be substantially represented in computer readable medium and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.

[0032] The functions of the various elements shown in the figures, including any functional blocks labeled as "processors", can be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions can be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which can be shared. Moreover, explicit use of the term "processor" or "controller" should not be construed to refer exclusively to hardware capable of executing software, and can implicitly include, without limitation, digital signal processor (DSP) hardware, network processor, application specific integrated circuit (ASIC), field

[0033] Software modules, or simply modules, can be denoted herein by any combination of flowchart elements or other elements indicating processes in execution steps and / or textual description. Such modules can be executed by hardware explicitly shown or implicitly shown in connection with appropriate software.

[0034] The drawings constituting a part of this disclosure are not to scale unless otherwise explicitly stated.

[0035] The following terms are defined for use in this specification, including the appended claims:

[0036] • "UHV seal" is defined as a seal through which small molecule gases, such as hydrogen, helium, and the like, cannot substantially pass. A UHV seal according to the present disclosure is capable of maintaining at least 10 -10 tor differential pressure, such as a UHV environment within a chamber sealed using only UHV seals. Examples of UHV seals suitable for use according to the present disclosure include compressible metal flanges, UHV compatible solder (e.g., indium, gold tin, etc.), welded joints, and the like. It should be noted that the definition of a UHV seal provided herein expressly excludes vacuum "pinch tubes", such as those used in prior art ion trap systems, in which a tube used to evacuate a chamber is sealed by mechanically crimping the tube and / or sealing the tube with solder after a vacuum pressure has been established in the chamber.

[0037] • "Non-UHV seal" is defined as a seal that is not suitable for use in a UHV deposition system and / or through which small molecule gases, such as hydrogen or helium, cannot substantially pass. Examples of non-UHV seals include pinch tubes, compressible gaskets made of non-metallic materials, non-UHV compatible solder seals, and the like.

[0038] Figure 1 A block diagram of an illustrative ion trap system according to the present disclosure is shown. Ion trap system 100 includes ion trap package 102, ion pump 104, ablation laser 106, and ionization laser 108.

[0039] Ion pump 104 is a compact conventional ion pump in fluid engagement with ion trap package 102.

[0040] Ablation laser 106 is a pulsed laser source suitable for providing an ablation signal 114 to material within ion trap package 102 to generate an atomic flux. As discussed below, optical access of ablation signal 114 to the material to be ablated is achieved by including a window in ion trap package 102. In the depicted example, ablation laser 106 is a Q-switched Nd:YAG pulsed laser with a wavelength of 1064 nm providing 8 ns wide pulses with a pulse energy of 0.3 mJ; however, other laser sources can be used in ablation laser 106.

[0041] Laser module 108 includes conventional laser sources for providing laser signals 116 including wavelengths suitable for ionizing neutral atoms within ion trap package 102, Doppler cooling and detection, and optical repumping. In the depicted example, laser module 108 includes continuous wave (CW) lasers with wavelengths of 355 nm, 391 nm, 399 nm, 370 nm, 638 nm, and 935 nm.

[0042] RF port 110 and DC port 112 are conventional electrical feedthroughs for implementing external electrical connections of RF and DC electrical signals to electrodes of ion trap 202.

[0043] Figure 2A Figures A through B depict schematic diagrams of a top view and a cross-sectional view, respectively, of an ion trap package according to an illustrative embodiment. Figure 2B The cross-sectional view shown in Figure B is taken along line a-a shown in Figure A. Figure 2A The cross-sectional view shown in Figure B is taken along line a-a shown in Figure A.

[0044] Ion trap package 102 includes ion trap 202 and enclosure 204, which encloses the ion trap within an ultra-high vacuum (UHV) environment.

[0045] Figure 3 Operations of a method suitable for forming an ion trap package according to an illustrative embodiment are depicted. Reference is continued to Figure 1 and 2A Method 300 is described with reference to Figures A through B and with reference to Figure 4 Method 300 begins with operation 301, in which ion trap 202 is fixed and wire-bonded to conventional chip carrier 206.

[0046] Ion trap 202 is a conventional microfabricated surface ion trap. Examples of surface ion traps suitable for use in accordance with the teachings of the present disclosure include the Sandia National Laboratories HOA 2.0 ion trap and the like. As will be apparent to those skilled in the art, a microfabricated surface ion trap includes a plurality of electrodes disposed in two one-dimensional arrays on a surface of a substrate such that the electrodes define a linear trap region TR between the linear arrays. A longitudinal axis of trap region TR defines a trap axis TA.

[0047] Electrodes of ion trap 202 are electrically coupled with bond pads that are wire-bonded to RF port 110 and DC port 112 (not shown in Figures A through B) to achieve a desired arrangement of RF and DC electrical signals at the ion trap. Figure 2A

[0048] Enclosure 204 includes a plurality of components, including chip carrier 206 and housing 208, which includes sidewall 208A and lid 208B. In some embodiments, housing 208 is a monolithic structure that includes a continuous portion that defines sidewall 208A and lid 208B. For example, in some embodiments, housing 208 is machined from a block of solid material, thereby forming a single continuous element that includes sidewall 208A and lid 208B.

[0049] ​In the depicted example, the enclosure 204 also includes windows 214-1 through 214-3 mounted in the sidewall 208B and a window 214-4 mounted in the lid 208B. The windows 214-1 through 214-4 are secured within the housing 208 via UHV seals 210-1 through 210-4, respectively, such that small molecule gases, such as hydrogen, helium, and the like, are substantially unable to pass through the windows and UHV seals. Preferably, the windows 214-1 through 214-4 are made of a single crystal material that also mitigates the diffusion of small molecule gases.

[0050] In the depicted example, each window is sealed to the housing 208 via a UHV seal that is made by first forming a braze joint on the window and then beam welding the braze joint to the housing.

[0051] At operation 302, the sidewall 208A is joined to the lid 208B and the ion pump 104 at UHV seals 210-5 and 210-6, respectively. Small molecule gases, such as hydrogen, helium, and the like, are also substantially unable to pass through each of the UHV seals 210-5 and 210-6. In the depicted example, each of the UHV seals 210-5 and 210-6 is a welded joint.

[0052] At operation 303, the chip carrier 206 and the partially assembled enclosure including the housing 208 and the ion pump 104 are loaded into the UHV assembly system 400.

[0053] Figure 4 A block diagram of a UHV assembly system according to the present disclosure is depicted. The UHV assembly system 400 is an alignment / joining system that is capable of aligning and joining separate components while they are under UHV conditions. The UHV assembly system 400 includes a UHV chamber 402, a pump 406, an alignment system 408, a joining system 410, and a load lock 404.

[0054] The UHV chamber 402 is an environmental chamber that is capable of maintaining a pressure of less than or equal to 10 -9 Torr.

[0055] The chip carrier, the housing, and the ion pump are placed into the UHV chamber 402 via the load lock 404, which is a conventional access through which parts can be loaded into the UHV chamber 402 without significantly degrading its UHV environment.

[0056] The pump 406 is a conventional UHV pump that is configured to evacuate the UHV chamber to a pressure of less than or equal to 10 -9 Torr.

[0057] The alignment system 408 is a six degree of freedom alignment system that is capable of achieving and maintaining high precision alignment between multiple parts.

[0058] At operation 304, a surface treatment is applied to at least one surface within the chamber 212, such as ion sputtering and the like. In the depicted example, multiple surface treatments are performed, including argon ion beam treatment, plasma treatment, and thermal treatment.

[0059] At operation 305, a getter surface 220 is formed on the lid 208B. In some embodiments, a conventional getter, such as a non-evaporable getter (NEG), is positioned within the chamber 212.

[0060] At operation 306, the chip carrier 206 is aligned with the enclosure 208.

[0061] In the depicted example, the chip carrier 206 and the enclosure 208 are aligned and joined such that the trap axis TR is oriented along the ion pump direction and the trap axis TA is oriented at an angle Θ relative to the propagation direction of the ablation signal 114. In the depicted example, Θ is equal to approximately 45° such that the ablation signal passes through the trap region TR at a diagonal.

[0062] Optical entry of the ablation signal 114 is achieved through the window 214-1, which allows the ablation signal to reach the material 218 in the crucible 216 to ablate the material and generate an atomic flux. In the depicted example, the material 218 is ytterbium (Yb).

[0063] In a similar manner, optical entry of the laser signal 116 to the ion trap 202 is achieved through the window 214-2.

[0064] In the depicted example, each of the UHV seals 210-1 through 210-6 is a laser welded joint. In some embodiments, at least one of the UHV seals 210-1 through 210-6 is a different UHV seal including a material suitable for use in a UHV system, such as but not limited to indium, gold tin, and the like, such as a compressible metal gasket (e.g., a copper gasket or the like), a brazed joint, or a UHV compatible solder ring.

[0065] At operation 307, the chip carrier 206 and the enclosure 208 are joined via the UHV seal 210-7. In the depicted example, the UHV seal 210-7 is a solder seal including indium. Formation of the UHV seal 210-7 completes the enclosure 204, thereby sealing the ion trap 202 within the chamber 212, where the internal UHV environment is equivalent to the environment within the UHV chamber 402. In other words, after operation 304 is completed, the chamber 212 contains an environment in which the pressure is less than or equal to 10 -9

[0066] ​In the depicted example, once fully assembled, the enclosure 204 has overall dimensions of approximately 130 mm x 100 mm x 70 mm. However, as will be appreciated by those skilled in the art upon reading the present disclosure, these dimensions are merely exemplary and the enclosure 204 can have any actual physical dimensions without departing from the scope of the present disclosure.

[0067] In the depicted example, the joining system 410 is an indium seal system configured to operate in a UHV environment and the UHV seal 210-7 is an indium solder ring. However, it should be noted that joining systems other than laser welding systems can be used to join components under UHV conditions without departing from the scope of the present disclosure. In some embodiments, for example, the joining system 410 includes a laser welding system, a soldering system, and / or a system for compressing compressible metal flanges, such as those used in MBE systems, ALE systems, and the like.

[0068] In some embodiments, the components of the enclosure 204 to be joined are provided with groove rings and frames that interlock when welded or joined via compressible metal flanges and / or UHV compatible solder to ensure a reliable seal.

[0069] It should be noted that while the enclosure 204 is assembled and joined with the ion pump 104 (except for the seal 210-6) prior to being placed in the UHV chamber 402, in some embodiments, more of the enclosure assembly is completed within the UHV chamber itself (e.g., at least one of the windows 214-1 to 214-3 and / or the lid is joined to the sidewall 208A, and / or the sidewall 208A is joined with the chip carrier 206, etc.). Furthermore, in some embodiments, the fully or partially assembled enclosure 204 is joined with the ion pump 104 when they are both positioned within the UHV chamber.

[0070] An aspect of the present disclosure is that the components of the enclosure are joined and the enclosure is sealed using only UHV seals while the interior chamber thereof has a pressure less than or equal to 10 -9 The pressure imparting embodiments offer significant advantages over prior art ion trap systems, including:

[0071] • elimination of unreliable pinch tubes; or

[0072] • enabling operation at temperatures higher than cryogenic temperatures (e.g., greater than or equal to -50°C); or

[0073] • significantly smaller overall ion trap system volume; or

[0074] • enabling an ion trap system without cryogenic pumps; or

[0075] • any combination of i, ii, iii, and iv.

[0076] For example, in illustrative embodiments, the chamber 212 has a volume of only approximately 2 cm 3 In some embodiments, the volume of the chamber 212 is not 2 cm 3 ; however, it is preferably less than 10 cm 3 .

[0077] At optional operation 308, the pressure in the chamber 212 is reduced to 10 -10 Torr or less. In the depicted example, the ion pump 104 is engaged to reduce the pressure within the chamber 104 to 2 x 10 -11 Torr or less.

[0078] It will be apparent to those skilled in the art that the quality of the vacuum in an ion trap system determines the lifetime of the ion chain. The rate of elastic collisions between residual background gas molecules and trapped ions is a key parameter for the trapped-ion quantum computer, as these collisions with sufficient kinetic energy transfer can significantly destroy the trapped-ion chain. In order to reliably maintain the ion chain over the time period required for quantum computation, the vacuum degree must be in the UHV range (preferably approximately 10 -11 Torr or better).

[0079] Another aspect of the present disclosure is that the pressure inside the chamber 212 can be measured (or estimated) by monitoring the behavior of one or more trapped ions.

[0080] Figure 5 An operation for a method for monitoring the pressure inside an ion trap system according to the present disclosure is described. The method 500 begins at operation 501, where a double-well potential is generated in the ion trap 202.

[0081] Figure 6A A simulation of a double-well potential according to the present disclosure is depicted.

[0082] The graph 600 depicts the ion potential as a function of axial position under several conditions, where the minimum of the height of the potential barrier between the wells W1 and W2 is significantly lower than the average energy transfer from collision events (i.e., the collision energy).

[0083] At operation 502, the potential barrier between the two wells is controlled. In the depicted example, the potential barrier height BH is controlled to 50 μeV, which is less than the average collision energy <ei> θ of approximately 1 / 40, the average collision energy is given by

[0084]

[0085] where m i and m m are the masses of the ion and background gas molecule in the trap, v is the relative velocity between the ion and background gas molecule, Θ is the scattering angle, and E m is the initial kinetic energy of the background gas molecule. In the depicted example, the ion is 174 Yb + and the background gas molecule is H2; thus, equation (1) provides an estimated average collision energy of approximately 2 meV <ei>Θ. Under these conditions, each collision event is expected to randomize the ion position.

[0086] At operation 503, the position of the single trapped ion is monitored between traps Wl and W2. In the depicted example, the position of the trapped ion is determined by imaging the ion position on an electron-multiplying CCD (EMCCD) camera to determine which of the two traps contains the ion.

[0087] Figure 6B A graph of the position of the trapped ion between the traps of the double-trap potential over time according to the present disclosure is depicted.

[0088] Graph 602 depicts a sample trace of the total EMCCD signal counts of the pixels in the regions in which the minima of the two potential traps are positioned (designated as region 1 and region 2), which indicates the ion position over time (i.e., the rate of transits).

[0089] At operation 504, the rate of ion transits between traps Wl and W2 is determined. This transit rate is extracted from graph 602. In the depicted example, the transit rate is 1 event per 32 minutes. The actual collision rate is expected to be about twice the measured transit rate, as the ions will eventually be Doppler cooled into either trap after a collision.

[0090] At operation 505, the pressure in chamber 212 is estimated based on the extracted collision rate. The relationship between the collision rate γ and the pressure in chamber 212 is given by:

[0091]

[0092] where P is the pressure in chamber 212, Q is the net charge of the trapped ion, T is the temperature, a is the polarizability of the background molecules, and ε0is the vacuum permittivity.

[0093] In the depicted example, γ = 1 / (16 min), μ ~ m H2 = 3.32 x 10 -32 kg, a H2 = 8 * 10 -31 m 3 and T = 300 K. Thus, the pressure P at the ion position is equal to 2.2 x 10 -11 Torr.

[0094] In some embodiments, the pressure in a UHV chamber is estimated based on the rate of reordering of ions in a chain of ions held in an ion trap.

[0095] Figure 7 Operations are depicted for an alternative method for monitoring pressure inside an ion trap system according to the present disclosure. The method 700 begins with operation 701, in which isotopes of ions having at least one property different from one another are selected for inclusion in an ion chain to be trapped in the ion trap 202. Selecting ions having different properties enables determination of the order of ions in the ion chain. In the depicted example, isotopes are selected to be 174 Yb + and 172 Yb + ions, which would appear as bright and dark ions, respectively, in the ion trap system 100. In some embodiments, the different properties selected for the isotopes are different from brightness. Examples of other properties that can be selected to distinguish isotopes according to the present disclosure include, but are not limited to, ion species, ion isotopes, and the like.

[0096] At operation 702, the collision energy required to induce an observable reordering event in the ion chain is estimated.

[0097] At operation 703, the selected ion chain is trapped in the ion trap 202. In the depicted example, the ion chain includes four 174 Yb + ions and two 172 Yb + ions. Note that the small difference in isotopic mass is generally negligible, as it does not significantly change the expected energy barrier of 2.2 meV.

[0098] Although multiple isotopes are included in the ion chain, only one isotope will be in resonance with the Doppler cooling laser (370 nm in the depicted example); therefore, the EMCCD camera will only detect this isotope. In the depicted example, 174 Yb + ions are selected to be bright, while two 172 Yb + ions remain dark.

[0099] To estimate this collision energy, the energy difference between (1) a first chain configuration in which the ions are aligned along the trap axis in their typical configuration and (2) a second chain configuration in which two of the ions have been pushed into one of the transverse axes is determined.

[0100] Figure 8A First and second chain configurations are depicted to estimate the collision energy for the six-ion chain of method 700.

[0101] When the same ions are at rest in the trap, the total energy of the chain is given by

[0102]

[0103] where m is the mass of the ion, ω x,y,z are the trap frequencies along the x, y, and z directions, R i = (X i , Y i , Z i ) is the equilibrium position of the i-th ion in the trap and Q is the charge of the ion.

[0104] In the depicted example, ω x,y equals 2.7 MHz and ω z equals 0.32 MHz. Thus, the energy difference between the first and second chain configurations can be determined to be approximately 2.2 meV.

[0105] Thus, it is expected that a reordering event can occur when an ion chain acquires more than about 2.2 meV of energy due to a collision event. This value is close to the estimated average energy exchange in a single collision event as given by equation (1) above. Thus, it can be expected that one of two collision events will result in a reordering event, since approximately half of the background molecules will have an energy greater than 2.2 meV.

[0106] At operation 704, the order of the ions in the ion chain is monitored via the EMCCD camera.

[0107] At operation 705, the time interval between ion reordering events is determined.

[0108] Figure 8B A histogram depicting the time interval between ion reordering events is depicted. Graph 800 shows the reordering interval times of ion chain reordering events recorded in 2 minute time bins over a period of 15 hours.

[0109] As shown in graph 800, 54 reordering events were recorded and the average reordering rate was approximately one event every 15.8 minutes. It should be noted that since some adjacent ion pairs are the same isotope, it is estimated that only approximately 2 / 3 of the reordering events were detected. Thus, a correction factor is applied to the recorded data, giving a "true" reordering rate of approximately one event every 10.5 minutes.

[0110] It should be noted that if every ion-molecule collision that results in a transition initiates a reordering event, then based on the collision rate of a two-ion chain multiplied by 3 to get a six-ion chain, a reordering rate of one event every 5.3 minutes would be expected. Assuming the required energy for a reordering-collision event is approximately 2.2 meV (which is similar to the estimated average energy exchange during a collision event), then it is reasonable that the measured reordering rate is about half of the collision rate.

[0111] At operation 706, the pressure in the chamber 212 is estimated based on the reordering rate of the ion chain.

[0112] It should be understood that the present disclosure teaches only some examples of embodiments of the application and that many variations of the application can become apparent to those skilled in the art upon reading the present disclosure, and the scope of the application should be determined by read claims.< / ei> < / ei>

Claims

1. An ion trap system, comprising: an ion trap that is free of cryo-pumping and disposed on a chip carrier; and an enclosure that encloses the ion trap in a first chamber, wherein the enclosure includes a plurality of components including the chip carrier and an outer housing, wherein the components of the plurality of components are joined by a plurality of seals consisting of UHV seals, and wherein at least one seal of the plurality of seals includes at least one of a welded joint, a compressible metal gasket, and a UHV compatible welded joint; wherein the first chamber has a volume less than or equal to 10 -10 the pressure of the cartridge; wherein the first chamber has an internal volume less than or equal to 10 cm 3 ; and wherein the ion trap system has an operating temperature greater than or equal to -50°C.

2. The ion trap system of claim 1, further comprising an ablation furnace.

3. The ion trap system of claim 2, wherein the plurality of components includes a first window.

4. The ion trap system of claim 3, wherein the first window comprises a single crystal material that inhibits diffusion of small molecule gases through the window.

5. The ion trap system of claim 1, wherein the enclosure includes a first surface that is activated to adsorb gas molecules.

6. The ion trap system of claim 1, further comprising at least one of (1) a getter material and (2) an ion pump.

7. The ion trap system of claim 1, further comprising: an ion pump joined with the enclosure via a first UHV seal.

8. A method for forming an ion trap system, the method comprising: positioning an ion trap in a first environment having a first pressure less than or equal to 10 -9 tor, wherein the ion trap is positioned within a chamber of an enclosure, the enclosure comprising a plurality of parts, and the chamber has an internal volume less than or equal to 10 cm 3 H. joining the components to the enclosure with a plurality of UHV seals, each of the plurality of UHV seals made by forming a braze joint on the component and electron beam welding the braze joint to the enclosure, the chamber open to the first environment; and forming a first UHV seal to isolate the chamber from the first environment while the ion trap and enclosure are positioned in the first environment, wherein the first UHV seal includes at least one of a welded joint, a compressible metal gasket, and a UHV compatible welded joint.

9. The method of claim 8, further comprising providing a second pressure in the chamber, the second pressure being less than or equal to 10 -10 T.​ 10. The method of claim 8, wherein the first pressure is provided such that it is less than or equal to 10 -10 Tons.​ 11. The method of claim 8, further comprising providing the enclosure such that it includes a window comprising a single crystal material that inhibits diffusion of small molecule gases.

12. The method of claim 8, further comprising surface treating at least one surface of the enclosure while the enclosure and ion trap are positioned in the first environment.

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